I recently had friends invite me to play a game of dnd with them and we ended up tossing around the idea of playing a merchant type character. I really like the idea, but don't know where to begin. What race would be good for flavor or in general, what kind of stuff i'd maybe do, or any tips in general.

Any race will work, merchants are pretty universal. Background is, well, guild artisan/merchant is the obvious choice. Class is going to be a more interesting choice. Maybe think through why you’re becoming an adventurer. What happened that you want to give up your merchant life and start killing goblins?

I could see something like a rogue or maybe bard, if you want to be a fast talker, there’s ways to make that work, and could fit well with a merchant.

Or you could go sorcerer if you want to be someone who suddenly discovers their magic power. Warlock if you made a deal with the devil (or something else). Artificer if you used to tinker on the back room and found some new uses for your hobby  

Paladin if you decide you wanted to make a promise to a higher power about something. Fighter because you used to have to beat up those kids who tried to rob you.

Really almost any class (wizard, monk, barbarian might be tough, but not impossible) can work, just decide what happened that you are closing the store. 

I playing a merchant noble currently as a PC warlock.  Warlocks are potentially great classes for a merchant, and I'd imagine a bard would be a similarly good choice.

Sorcerer could work too (I don't know if your game has started yet lol) but that gives you charisma, which is good for merchants, and your backstory is easily just "oops, used magic accidentally and had to leave the guild" or something similar- after all, merchants who can't control magic powers don't really get too many customers. (I'm assuming wild mage, or maybe just the character has worked out how to control it by now)

In addition to the Guild Merchant/Artisan, there is also the Failed Merchant from Acquisitions, Inc., the Clan Crafter from Sword Coast Adventurers Guide, and several options from Ghosts of Saltmarsh.

My suggestion is pick a starting point and work from there. If you start with a race, then you can let they're strengths inform your decisions. Dwarves have produced proficiency in Smith's Tools, Mason's Tools, or Brewer's Tools. You can select one of those and then consider what that might mean. Smith's and Mason's are typically strong, so a fighter, Barbarian, or a Paladin might be your class with one of the mentioned backgrounds. Maybe, with the Brewer's tools, you were a hermit that was perfecting the right recipe for your brew and now you want to travel the world and make a fortune selling it. Only problem is you need funds to get you started and you just happened to hear about Adventurers making large chunks of money. 

You could start with the Class and let that inform your decision. Let's say that Artificer speaks to you, and you decide that Rock Gnome sounds like a good idea because of the intelligence boost and Artificer's Lore and Tinkerer traits. You notice that tinkerer is one of the options for Guild Artisan and select that.  You see that the Community Ideal suggests providing for the security of the community and as such, your gnome decides to sign up with a mercenary band or something to help secure the area. 

Or, you start with the background, noticing that there is the Sailor option in the PHB to go with the Shipwright, Smuggler, Fisher, Marine, et al. from the Ghosts of Saltmarsh. You decide to select one of those, then decide that the character is going to have a touch of a pirate feel. You are now a Swashbuckler Rogue, or will be at third level. You notice that Rakish Audacity gives you an initiative bonus equal to your charisma modifier, and you decide to go with a Tabaxi because the bonuses match what you are looking for and because the idea of a cat person that hates getting wet but works that close to the sea sounds fun and like a solid reason for the character to decide to move on, if only to find some magical item that will keep them from getting wet. 

Finally, if your DM allows the Tasha's race options, you can customize more fully. Perhaps the Failed Merchant idea appeals to you, but you like the idea of someone who couldn't focus on an idea long enough to succeed. Mountain Dwarves have lots of options for tools proficiencies, thanks to options from the background, the option mentioned above, and the Dwarven Combat Training and Dwarven Armor Training that you can change anything that you don't need or that is redundant from your class to a tool proficiency. They start with +2 strength and +2 constitution, but either can be repurposed to something that you need for your character. Maybe a drunken Bard that drinks enough to even get a Dwarf drunk, but he's knowledgeable about lots of skills and more dexterous than strong and more charismatic than hearty (part of the reason why he gets drunk more frequently than most dwarves).

Or you have Lizardfolk Cleric that had become a Death Cleric or a Grave Cleric because of his desire to be able to grub on the job. He could be an acolyte, could be an undertaker, could just be a Noble who became a cleric to be able to hide his desire to eat things and is morbidly satisfied being with dead and decaying creatures. There are lots of options available. 

I think a Tortle would be really fun for a traveling merchant character. They have a sort of Wanderlust as part of their racial features, and their shells let them easily survive in long travel without needing to carry tents or anything. I'd actually recommend a Beastmaster Ranger as your subclass. Ranger makes sense for a character that's on the road all the time... just enough spellcasting to help you in key moments. Beastmaster, especially with the update in Tasha's, gives you a reliable companion to travel with you. Also from Tasha's you could replace Natural Explorer with Deft Explorer to give your merchant expertise in Insight to help avoid getting swindled, and even learn a couple extra languages, which are always useful for merchants.

Tortles give a boost to STR and WIS, in case your DM doesn't allow the customizable lineage (or whatever it's called) from Tasha's, which works well for a STR-based Ranger character... not very common, but there's nothing that says your character needs to be DEX-based just because they're a ranger.

Quote from TransmorpherDDS >>

I think a Tortle would be really fun for a traveling merchant character. They have a sort of Wanderlust as part of their racial features, and their shells let them easily survive in long travel without needing to carry tents or anything. I'd actually recommend a Beastmaster Ranger as your subclass. Ranger makes sense for a character that's on the road all the time... just enough spellcasting to help you in key moments. Beastmaster, especially with the update in Tasha's, gives you a reliable companion to travel with you. Also from Tasha's you could replace Natural Explorer with Deft Explorer to give your merchant expertise in Insight to help avoid getting swindled, and even learn a couple extra languages, which are always useful for merchants.

Tortles give a boost to STR and WIS, in case your DM doesn't allow the customizable lineage (or whatever it's called) from Tasha's, which works well for a STR-based Ranger character... not very common, but there's nothing that says your character needs to be DEX-based just because they're a ranger.

 And the dex isn't as needed with the Tortle since they have 17 AC anyway. Dexterity saves are a different story.

My Bard has a sideline occupation where he wishes to create an import-export company, but he is doing this to create a "front" so he can operate a spy network.  So he doesn't do this to avoid adventuring or to earn money in lieu of adventuring.  But he does hope to derive some benefit from the spy network.  That will depend on the DM.  Good luck.

I’d be a Tabaxi that imports pepper to the northern regions of faerun.  

For products, just look at IRL imports from a couple hundred years ago.

pepper, cinnamon, tobacco, tea, coffee, sugar, bananas, etc.

Quote from HeathSmith >>

I’d be a Tabaxi that imports pepper to the northern regions of faerun.  

For products, just look at IRL imports from a couple hundred years ago.

pepper, cinnamon, tobacco, tea, coffee, sugar, bananas, etc.

 An importer that got tired of getting robbed on the road, so s/he learned how to fight to help defend the business. With that extra skill, there are now new areas available to explore to find new goods to trade.

I say warlock. Merchant was having financial difficulties and their business was starting to fail. Made a “deal with the devil” and their business started to thrive. Eventually the patron wants something so you pack up your gear and hit the road to your first adventure.

i am trying to play a game where i adventure but be more of a wandering trader and still sell things as we go and make my charisma really high so i sell stuff to people for exorbitant prices

on top of this i can also sell useless items i get from adventuring on top of the items my supplier gives me

The key to being a merchant is finding something in demand in one place and finding a good inexpensive supply in another.  Then you buy the inexpensive supply, pay to have it transported to the demand location, and sell it at a profit which accounts for the transportation costs and still provides you a handsome profit.  Now, it is even better if your transportation folks can take something back and sell that for a profit.  Then you make money on both trips.

After this is worked out, the DM throws a hazard at you, such as bandits robbing a shipment.  Now you have to deal with the bandits.  Do you hire guards that eat into your profits?  Or do you track down the bandits and rob them?  Or do you hire the bandits to be your security force and maybe they raid other caravans instead?

Then the DM throws another curve ball at you.  Maybe insects infest a shipment.  How are you going to make that up to your customers?

So the qualities you want seem to be the qualities of a Bard.  But your bard needs help in the form of muscle.  So you hire barbarians, fighters, and rangers.  And when other kinds of problems come up, you hire spell casters or a Rogue to infiltrate a competitor's organization.  And off you go.

As a dwarf you could travel about selling your metalwork, jewelry, alcohol, or you could higher yourself out at as a smith or mason.

A goblin might be a fun adventuring merchant. You joined the party in order to collect loot to sell as your wares.

A tortle is also a good fit. You could trundle about with your trinkets and wares slung over your shell.

I had a friend who played a rice merchant once. He walked about with a pot of fried rice on his back and sold it during his free time.

There are all sorts of ways to play the adventurer/merchant (as reading through this thread shows). So here are some other thoughts. Traveling merchants work as adventurers  because both are constantly on the move. That is often because they feel either a wanderlust or “out of place” everywhere. To me that says Halfling or Half Elf (or anything given wanderlust). This also means they are often outside alone and that says ranger or bard  (or a ranger or bard based multiclass). If you use the UA1 backgrounds (if the DM allows) you get 2 skills and a tool proficiency. That sets several possibilities in motion three I like are:
1) tinker’s tools - you are a traveling tinker fixing things for pay in each community you come across. The nice thing here is that tinkers tools is a sort of jack of all trades thing so you can do a little woodworking, a little blacksmithing, a little white smithing a little gold smithing a little jewelry making pretty much a little of anything. Especially as a bard with jack of all trades this works well.
2) Herbalism - medicinal herbs as well as cooking spices - not only can you brew and sell healing potions (&poisons) but there should always be a need for the various herbs and spices you collect along the way as well. You will have to role play the collection and trading with the DM of course but could give the DM lots of hooks as well.
3) jewelers tools - matched with ranger’s expertise in nature this could be someone who hunts for gems and precious metals then turns them into jewelry for sale. Why adventure? Because dungeons typically have both gems already free as well as gold, silver and copper free for the taking (if you survive) this calls for the DM to translate some of the coinage into gems but that isn’t really hard. 
There is a fourth ranger based option as well - furs. Your merchant hunts and traps selling the furs and pelts periodically.  Or maybe a combination of several of these . I could see a ranger/ bard multiclass half elf with all three of these traveling around and getting involved in adventuring as a way to improve? Their survival chances. Or putting a group together to do general exploration and dungeoneering in a region like FR’s High Forest that is both wilderness and “filled” with ancient elven ruins.  

I'm running a Yuan-ti sorcerer as a gem merchant from a merchant family. This is a homebrew evil campaign.

Guild artisan/merchant background is a good merchant background since you get tools (which one depends on what kind of merchant you are ... and it even has a list of guild businesses you can use to select the kind of merchant you are. There is also a Baldur's gate guild artisan/merchant background.

Artificers are also natural merchants, make stuff and sell it. No?

An interesting resource/reading for a merchant adventurer is Louis La’More’s book “The Walking Drum”  set in roughly 1100’s Europe (Brittany to Spain to Russia & Byzantium) and the Middle East (Turkey, Iraq and Iran) - plenty of adventure and plenty of trade.

I'd play a Changeling Rogue drug dealer selling Dreamlily while constantly changing appearance and voice on the move, only to be known as ''Reverie''.