Adventuring gear?

If you’re taking gold instead of default gear in a campaign, what gear do you usually buy?

Namely, in a campaign where you’re starting at higher level and already have weapons accounted for?

Explorer’s Pack? Potions? Other?

If you have weapons accounted for, potions are definitely a great option. I could see a 5th-level character (just assuming here) buying a few potions at DM discretion, which could turn out useful in the sometimes more remote/difficult Tier-2 encounters. Like a Potion of Water Breathing (or whatever it's called in the new edition) could prove useful in the case your wizard doesn't have the spell prepared, and you need to get underwater quickly. Could be useful. This can also apply to uncommon magic items - some can prove useful, and they're at reasonable prices - even each village has that one special item that was passed down from generation to generation and has saved the lives of [insert names here]. 

Explorer's Pack I could imagine, too, especially if you don't have some of the items. Those things can prove more useful than people think. 

That's pretty much it - potions, packs, & uncommon magic items. I dunno - maybe just save it if you can't figure out what to buy. It'll come useful when you dent your chain armor and need a repair. Don't underestimate (or overestimate) the value of carrying a few gold around. 

(You can also bribe the guards to look the other way.)

Gear every adventurer should have:

1) a light source - lantern, torches etc...
2) at least 1 rope - endless uses from tying up baddies, to helping allies climb stuff, to pulling allies out of harm's way, or lifting / dragging stuff, or pulling stuff from a distance. (optional) a grappling hook to go with it.
3) some oil - also tons of uses, setting stuff on fire, loosening hinges/locks, creating light in lanterns.
4) any sets of tools they are proficient in using
5) Sleeping gear - tent, bedroll
6) Eating gear - mess tin, waterskin, rations, tinderbox
7) something to carry stuff in - e.g. bag / backpack

Beside Explorer Pack, useful adventring gear i may take depending on character;

• Antitoxin
• Crowbar
• Healer's Kit
• Lantern/oil
• Manacles
• Portable Ram
• Poison
• Signal Whistle

Some others I've thought up (and the other ones I already thought of):

• Training in skills/tools (this actually is more useful than it seems)
• Acid
• Armor (better AC armor) 
• Uncommon magic items
• Potions
• Packs (Explorer's, Dungeoneer's)
• Enchantments (a 1st- or 2nd-level spell on some of your gear can prove useful, even if it's temporary)
• Torches (obviously), Lanterns, other light-creators
• Kits (yep, @Plaguescarred, I like the Healer's Kit idea in case people don't have Spare the Dying or other spells)
• Honestly, basic services. Repairs, refittings, forgings, and the like. Get your dented armor fixed, or some stuff you've found on the travels refitted by the local tailor, and/or getting a sword made for your particular size? Just everyday artisanship services are useful in quite a lot of cases, surprisingly. 
• Anything else, anyone?
• (Oh - I thought about another one, less for spending money but maybe for acquiring more of it...) --> GAMBLING!!! (always the #1 choice for all of my characters sadly - I have lost a lot of (stolen) party money that way)

I generally go on the assumption that each party member will have basic gear. however, you want to define that. Tinderbox, back pack, shaving kit (if needed), mess kit, torches/lanterns.

However, I do also want them to specify more specialized things such as rope, pitons, spikes, etc.  Things could end up with a limited number of uses and then they do not have them anymore

All the aforementioned standard items, plus:  Caltrops!  Marbles.  Beef jerky.  An empty mason jar.  

Beef jerky is w

I'm probably stupid, but why the mason jar? Just for storing things?

Yeah. Sure. You never know what you're gonna find. Maybe scoop up a bit of gelatinous cube. Maybe a cool looking spider. It's better to have it and not need it than need it and not have it.

I’d probably spend the gold on things that are harder to get during the adventure, like useful potions, utility items, and some backup supplies. If weapons and armor are already covered, having tools that help the whole party usually feels like the best investment.

Depends on your level.

Anti-toxin is always a good idea.

As a DM I rule that starting magic items must be from the DMG/PHB.  That is my house rule.

Common = potion of healing or spell scroll (1).  Wizards may use a spell scroll to learn an extra spell as part of their back story.

Uncommon = +1 weapon/shield/cloak of protection etc.  3rd level spell scrolls learned before game.

Rare = +1 armor / ring of protection  (Elven Chain for wizard types) 5th level spell scroll learned before game

Very Rare = +2 weapon /shield/Wand of war mage etc. or 8th level spell scroll learned before the game

I made a basic things list and then add to it depending on my class.

Magic items and or spells add to or reduce the list.

Magic items and or spells improve the things on your list.

Assuming you have the free encumbrance (or a bag of holding):

• 11' Pole
• As much rope as you can carry, and a ball of twine/string.
• climber's kit and grappling hook
• block and tackle
• Caltrops and ball bearings (multiple of each).  Prioritize caltrops at higher levels.
• Spikes and a hammer.
• Mirror on an extendable rod (if nothing else, it's in a thieves kit)
• Acid (if you can't pick a lock, melt the bolt)
• 10' ladder (in the cart or bag of holding)
• blanket, sleeping bag, and tent (preferably in the cart or bag of holding)
• Iron Rations (unless you have someone with goodberry, and even then... just in case)
• blasting powder / explosives (setting permitting).  (I'm thinking more for 'excavating' then damage.  Blasting Powder only affects creatures RAW, but most DMs would probably allow it to damage objects).
• CHALK!
• Paper and pen.  (Someone's mapping the dungeon, right?)
• Light source and tinderbox.  (Even if you have darkvision, you can't generally read text written on the wall with darkvision).
• Crowbar
• Shovel
• Water flask
• Perfume (for social situations, including if a humanoid monster is willing to talk)
• Portable Ram
• A cart, covered wagon, or similar vehicle with appropriate beasts of burden, or at the very least some donkeys as pack animals.  You need to cart your loot from the dungeon to town somehow, and larger items you have a hard time carrying with you can live in a cart until you need it.

Spells can replace some of these, if your party has the right ones.

I always take pure cash and buy individual items.  The issue is usually figuring out what a Str 8 character can actually carry.