Different guilds will require different things for you. A casual guild is probably a good start as there aren't expectations on times you will be available and other things like that.
Personally, I have more friends that I made through PvP then members in my guild. I did my first HM last night (Hardmode Flashpoint that you can do at 50) with 1 guild member and 2 friends through PvP.
So while joining a guild usually means you can get assistance from other people, its not neccessary. In fact you can even just ask in /general if someone can help and might get lucky. I was doing a class quest on Dromund Kaas in my 40s and helped a level 12 guy with his class quest.
I have made more friends in this game in the first month then any other MMO I played for years for some reason.