Welcome back!
I can’t help you with the guild issue. I find this myself. There ARE guilds that are good for people who want to tryhard, get significant progress, and take the game seriously. I’ve been in a couple. They are kept together by the shared need for a reliable team to make progress.
However, for people who don’t want to make that commitment, there just isn’t enough holding the group together, and they fall apart as people come and go.
Further, as Sinstre said, a lot of communication has shifted to Discord, and Blizzard have been deprecating guilds since Mists. Also, the ability to group across realms has weakened the social fabric of the game enormously.
I don’t say that guilds of the type you want don’t exist; they are just not common. You are on the very best realm to find one, though, so you have that going for you.
Blizzard’s “Guild Finder” is entirely useless.
I’d keep an eye on the AD forum https://eu.forums.blizzard.com/en/wow/c/argent-dawn/190 and see whether anyone posting is in a guild that might be interesting to you.
As for
well, this forum is not a guild, but you WILL find help here. 
Do please just ask!
Let me give you a quick rundown on your near future.
You need to get to 60 AND complete the quest chain through the four zones of Shadowlands.
At 60, you can and probably should buy item level 229 Green gear at the Auction House as soon as you can afford it. You don’t NEED to,but it will make your early-60 days more comfoirtable. You can grind some gold, if you need to, as follows:
Heart of Fear LFR farm
Talk to the Raid Finder Storyteller in the Lorewalkers’ place above Mogushan Palace in Vale in Pandaria. Choose The Dread Approach (first wing of HoF).
Enter and kill all trash and the first two bosses. Right-click your portrait, choose Leave Instance, and keep re-entering until you have done your 10 per hour. Takes mayve 20-30 minutes for 10 runs once you have developed a rhythm. You will get vendor trash and auctionable Motes of Harmony.
From 10 runs of the instance, clearing the first boss and all trash before the second, I got
1,876 gold after vendoring all Greens (you won’t sell them at Auction)
119 Motes, worth 17.42 each at the AH today, so 2,072 gold there.
13 Lockboxes, worth nothing if you vendor them, but maybe 40 gold each if you have a Rogue that can open them.
2 pets, that might theoretically sell for a couple of thousand gold, but will probably be hard to shift.
Brann Bronzebeard, in that room, will act as a vendor for the Greens you want to vendor. Motes of Harmony sell fast on the cross-realm AH.
So for the half-hour, a fairly safe 4,000+ gold.
Wait until your ten instance per hour limit expires, and repeat as much as needed.
Also at 60, you will go to Oribos, where you will choose one of the four Covenants. I suggest Night Fae for a Druid, unless you have something specific in mind.
You will go to your Covenant, and have to do a mess of paperwork in the form of quests to establish yourself there, start your Covenant Campaign, choose a soulbind (see icy-veins.com for advice) .
You will get Flying when you hit Renown 45 with your Covenant. You get Renown through doing your Covenant Campaign, doing the daily Callings (set of quets you get each day for one of the zones), dungeons, Torghast runs, Bonus areas in the zones, and just about everything else.
You will also be sent to the Maw and from there to Torghast. DO NOT spend more time than you need there. All you need from the Maw is an introduction to the Runecarver in Torghast. He will provide your Legendary, if you choose to get one. The Maw is commonly considered the worst zone ever, and gives nothing useful now.
Korthia is the zone after the Maw, and is also dead at this stage of the expansion. You will get a quest to go there, but probably don’t need to. You do get the ability to mount in the Maw during the intro to Korthia, so you might want to do that, but it’s entirely optional now.
Zereth Mortis is the place you should open up, if you are doing that at all. 229 gear will let you get around fairly comfortably, and the Zereth Mortis Campaign leads to your second Legendary, Unity. It comes as a belt, but you can aslo earnm a version that can be inscribed onto any slot.
Search for any of these terms on Wowhead.com and look for a Guide, if you want to learn more, or ask specific questions here!
So your path is:
- Get 60, finish questline in all 4 zones.
- Buy some 229 Green gear at AH.
- Choose Covenant. Get established there.
- Do Covenant Campaign for Renown to get flying.
- Do the Maw and Torghast up to meeting the Runecarver.
- Go to Zereth Mortis, follow the quests there.
Dungeons are a whole 'nother story since WoLTK. Ask if you want to know!