I want to get good at this but I always run into a couple problems when I try

Every time I play regular people immediately lock in to what they want to play and I am stuck either making everyone hate me by playing something we don't need (I cant jungle and have no idea how). Or play some champion I either do not like or do not know. Should I just ignore all the people with the rude attitudes and play what I like?

I have a problem deciding how to spend my gold and how much offensive items I should have before I purchase defensive etc.

I usually play Diana, Akali, Zyra (pretty much Ap) and the occasional Miss fortune.