Quote from Yurei1453 >>

A Silent Image of a big bloof of fog - or sudden profusion of tall grass, or any other "concealment-not-cover" form of obscurement - is realistically no different than a regular Fog spell...save that you can see through it because you know it's not real. 

Exactly, meaning you get Advantage and your enemies get Disadvantage, because Fog Cloud provides heavy obscurement. Sure it's easier to overcome than Darkness, but should provide cover for a turn or two. After that, be tricksy, change it up, move the combat and change your illusion to something else. Force them to have Disadvantage again or at least waste a turn to make their Investigation roll again.

Solid combat advice for a warlock, Yurei.

Quote from 20kernsd >>

Thanks for the advice everyone. I do see that feylock isn't the best for buffs and is more about social trickery and I will utilize that quite a bit, but it's going to be a more combat focused campaign, so I have to balance that out with some good utility or buffs and debuffs, so I'm useful to the party in combat. I fully realize that I'm going to be weaker than the party in combat, but I don't want to be completely useless. I also have no idea how to build an effective warlock since this is my first time playing one, and most of the guides/builds for warlock I found were for other subclasses. There's also the problem of short rests, because every other party member gets nothing but hp back on short rests they're not going to want to take short rests unless we're badly injured. That makes my build even less effective. I know personally as a DM that I try to not give short rests in the middle of dungeons or combats because it allows players to get back hp and makes every other encounter going forward easier because of that. 

 Do keep in mind that Druids get Wild Shape uses back on a short rest. Since Symbiotic Entity runs off of Wild Shape uses, the Spores druid will likely want regular short rests, too. This is particularly true since you don't have a dedicated healer (unless you're counting the druid) and Wild Shape/Symbiotic Entity will likely be the primary method to mitigate damage. 

That said, don't discount Repelling Blast because you'll have two front liners. You don't have to push your targets back if you don't want to. Being able to push creatures off of your front lines allows them to disengage for free if they need to (or at least be targetted by fewer OAs), gives you extra time if enemies slip past and target you, and allow you to push creatures into optimal bunches, particularly useful considering the Spore Druid's "Aura". Not to mention the possibility of pushing them over cliffs or other such shenanigans. It can be used off of every beam whereas the other EB movement invocations only trigger once per attack.

Something that you may want to look into is Inspired Leader feat to stiffen up your party. The Temp HP won't stack with Symbiotic Entity and the Druid would lose the Temp HPs you give them when Symbiotic Entity is activated (otherwise they'll lose the Wild Shape use for nothing and not gain the benefits of Symbiotic Entity).

If you feel like Multiclass is necessary, talk to your DM about Druids and metal armors. Hide is not worth the multiclass and would therefore leave you to the other benefits of Druid to make up for it.

Cleric would be a much better option to give you medium armor, more spell slots and cantrips, and give you many more support options. Bard could be a good option as well, though you would need to go 3 levels to get a subclass with medium armor.

Cleric does have Warding Bond to help stiffen up the Druid more. Life makes your heals better, while the others offer a wide variety of support options.

Well, assuming we get ample short rests I'll go full warlock, as I don't want to multiclass until I'm at least a 4th level warlock that should give me enough time to decide whether to multiclass or not.

Quote from Ophidimancer >>

Quote from Yurei1453 >>

A Silent Image of a big bloof of fog - or sudden profusion of tall grass, or any other "concealment-not-cover" form of obscurement - is realistically no different than a regular Fog spell...save that you can see through it because you know it's not real. 

Exactly, meaning you get Advantage and your enemies get Disadvantage, because Fog Cloud provides heavy obscurement. Sure it's easier to overcome than Darkness, but should provide cover for a turn or two. After that, be tricksy, change it up, move the combat and change your illusion to something else. Force them to have Disadvantage again or at least waste a turn to make their Investigation roll again.

Solid combat advice for a warlock, Yurei.

 
Want to make sure your enemies don't try and fact-check your Silent Image by poking a finger through it?

Make it the image of a swirling cloud of tortured, silently wailing ghost-soul-skulls, or a bank of the most evilly noxious-looking, clearly hypertoxic vapor you can imagine.  Something that's so obviously and apparently horrible and unhealthy that nobody will want to go near it, let alone investigate it.  This one can not only offer you cover, but it can fox dumber foes from following you through a door or provide a few precious moments' respite from a sudden horde of attackers.

In addition to how potent Eldritch Blast is in combat, especially when you add Hex and Agonizing Blast on top of it, keep in mind that you’re one person in a team. If the three of you make decisions about how to level up as a group you can all build on each other’s strengths and weaknesses which should result in you being much more effective as a team than you will be if you make those decisions without working together. 

One of my suggestions is try to figure out how your warlock and the Druid can work together to give the rogue opportunities to get his sneak attack damage. And if you stay out of melee, you’re probably better suited to cast Faerie Fire than the Druid is because you’ll be getting hit less often so you won’t need to make Concentration checks to keep the spell going. 

Feylock isn't the best supporter in the game but it's not the worst either. Your best support is going to be controlling the combat.

You're definitely going to want eldritch blast.  Don't waste your second cantrip on an AC attack like chill touch.  You'll want either a save attack such as toll the dead or, a utility cantrip.  Remember, that you will also be getting 3 cantrips from any class (you said tome pact IIRC) when you hit level 3 so plan accordingly.  Personally, I am probably taking EB and minor illusion as my class cantrips at level 1.

For spells, with your limited spell slots, you want to pick concentration spells, and spells that scale since your spell slots are all highest level.  The exception to this is here at level 1, I am definitely taking sleep as one of my spells because you can end fights with it.  I'm a fan of hex, but in your case, I am probably taking sleep and faerie fire...and I will rarely cast faerie fire.  I won't keep sleep forever but for the first few levels it will make a huge difference. 

When you get to level three and take tome, you definitely want find familiar.  Pick an owl.  There's a ton of things you can do with this, you won't regret it.  For cantrips I am probably taking guidance (definitely if the druid doesn't have it), prestidigitation, and toll the dead.  I will /rarely/ choose toll the dead over eldritch blast, but occasionally, you'll find it's nice to have.

Thanks for the great advice.

I think ultimately, as the utility Infielder of the party (baseball reference, meaning a player who plays multiple positions), you will have as much out-of-combat utility as in-combat. So make sure you get to maximize non-combat situations and use of BoAS. Identify is definitely going to be good, and depending, your charms with Mask of Many Faces is definitely a good option. In combat, control the board and debuff or confuse the toughest foe. You won't kill a bunch of enemies, but you can nerf the big bad.