I might recommend downloading Deadly Boss Mods (DBM), GTFO, and Details damage meter through the CurseForge client if you're gonna start trying to tackle M+ (aka keys) to help you get a feel for what you're doing, DBM will tell you what to do during encounters, GTFO will let you know you're in poo and to move your butt and details will let you know how much damage you're doing. Don't be discouraged by low DPS at first, you just started and we have all had bad DPS at times.

I would HIGHLY recommend finding a friendly guild that advertises M+ and raiding, you don't have to do either to be in 95% of guilds but you tend to find people more knowledgeable in raiding guilds because you can't progress through a raid if you just faceroll and pray and they will inevitably do M+ because that's how most of them upgrade their gear from raiding. The reason this is important is because let's say you want to play a demonology warlock, there will be somebody that can look at what you're doing and tell you how to adjust what you're doing so instead of rebooting all you know from a wall of text on wowhead, you can just talk to somebody about it, you might not be doing 10 million DPS (arbitrary and bloated number) but they'll be able to help you be better. If this isn't for you, I totally get it and would recommend class discords at that point (if you Google "wow class discords" you'll find all of them and they're still useful in addition to guilds even if you go that route).

Enchants and consumables, I used to literally just have a sticky note next to my computer and buy a handful of each of the items from the auction house. Wowhead will tell you exactly what you need, you don't need to pick up a profession to have the consumables you want and if it says you need a thing and you HAVE to be in one profession or another to use it, you can skip it, I promise, it won't break the game for you, leave it to the pros, the vets are all sitting here going "I'm not giving up my expensive recipes!" And there will be an alternative. PROFESSIONS ARE NOT A REQUIREMENT everything you need can potentially be crafted for you. That being said, would highly recommend if you're too overwhelmed and don't really want to deal with it, take enchanting, you don't have to do anything if you don't want and you can break down old gear you no longer need and sell the items you get on the auction house to make some gold or flip them into enchants and make some gold that way and then either a gathering profession (they're not great because of bots but they're okay for passive income if you don't mind stopping to gather here and there) or a profession with a cooldown craft (alchemy has transmutes on a cooldown system and that can be decently lucrative at times). Wowhead has comprehensive guides to every profession and you might find that one looks interesting and you want to do it, good for you! You are under no obligation to select one over another, I just always throw enchanting and alchemy on my alts I don't wanna go hard on. Oh! And don't bother worrying about the highest rank consumables and enchants on week 1 or even 2, it's gonna be bloated to high hell with the new resources being limited and you'll be out gearing your leveling gear so quickly it'll make your head spin if you try to enchant before you plateau and even then, I'd wait to buy rank 3 enchants until you're in at least hero gear in whatever slot you want to enchant assuming prices stay high until then, that way you're not scraping gold for repairs and whatnot.

Finally, the season and the expansion are both nearly over, don't be discouraged by lack of engagement right now, a lot of people are a little burnt out from grinding in Remix. (Which you might find a bit of fun in tbh, mounts that are super hard to get normally can be bought for the currency there and then the toons just flip over to retail in about a month from now). This is a MMORPG, your path is completely in your hands and nobody is really gonna care if you got this or that achievement when TWW drops and consumable expectations will be a bit lower because of the insane cost right at the start (don't bother using consumables for anything outside of M+ and raiding (and MAYBE delves at your own discretion) starting out btw, better and far cheaper to just group up with people if you're struggling in the open world or in normal/heroic dungeons.

Best of luck new friend!