Casual guilds are always recruiting. That’s almost the definition. Finding one you like is the trick. You should specify Alliance or Horde, and watch your realm choice, as well of course.
Check out Communites, like cross-realm guiilds. Here are two that are full of nice people:
If you’re starting now,
get Friendly with all three reps on your faction while questing to 120 in BfA, and do your three Foothold quests, and your Island tutorial quest, to activate your Flight Master’s Whistle
Hit Nazjatar and then Mechagon, new daily zones, ASAP at 120 for gear
Nothing special. All classes are due for a rtevamp next expansion, so the future is anybody’s guess.