Okay, I just want some advice

I'm not sure if I want to join a band yet, since 2 of the bands that I know told me that they're good and they want me to join their. I played with one, all they knew was Canon Rock, a little metal songs (Like Escape The Fate).
We played with our teacher (Talented Keyboardist

). We couldn't play any good songs because the guitarist and drummer would go out of the room when they got bored (Meaning, me and my teacher played some 12-Bar or something they didn't know.)
They don't know this, but they think they're really good.. I wanted to tell them to learn the basics, but then that would be rude of me, since I know nothing about drums. I am also a beginner, since I've never actually joined a real band yet (Just Jamming bands).
My brother has seen the other band play, he told me I have to wait before joining that other band so that they could improve. (Well He really said: Don't tell them this: They Suck.)
And as a bassist having small hands, I think I'm no better than the bands that want me in. My teacher said I'm really good because I can widow, I still am not sure if I should join either or neither band.
Anyone advice on what to do with my musician life? Please don't flame me, but does playing Dream Theater help me?
I also want to ask a question:
I've been plaiying bass for 3 years (Though I kinda stopped at the 2nd year.) I've never actually joined a real band.
How do you guys get experience? Do you just play at home until you're ready or do you and your band practice and practice together? Not sure I'm ready enough to join a band yet
PS: If any of the things I've typed seemed like I'm arrogant sorry..
Advice please:





