Every action you do and every party you make will have a reaction by everyone else who's in it. The intimidating thing can be if you're new to the content, you have to show improvement along with everyone else, and be open to sharing what you've learned, no matter how obscure. The other thing is resolve. As long as there is someone new to your group that wants to learn, feel obligated to stay with them the whole duration of the timer (unless gear breaks). Of course, there are exceptions to that rule, but it shows how true your intentions are and you pick up friends VERY quickly and get asked to help out again.

There's no RULE for how long to stay in a PF group, but be ready to show a lot of patience! The longer you practice with a single group instead of ragequiting and picking up a new group, the more development and understanding you'll see.