I don't think you really need to have a guild until you are 60, pre-60 you just need a good few mates on your friend list that are around your level and play the game as much as you guys do.
But really, getting to 60 is everything. I thought i was going to play this game less when i hit 60, i have played it more. There is so much to do at 60 it's unreal. Molten Core is so much fun !
I'm too addicted to this game right now.