Its all about finding what YOU like to play. You don't want to play what is simply needed, because once you get locked down in a team you're pretty much going to be playing that role ALL. THE. TIME. If you dont enjoy the role, the game isnt going to be any fun for you...and thats what its all about

As for champions...play whomever you please! There are top tier champions yes, but any champion is viable if you get good enough with them. Hell, Poppy is considered useless in most temacomps nowadays, and theres a 2500 elo player who does nothing but player her every single game...and he wins. Just find what you like, and go with it!

Aw man. Bean's post reminded me.

When I first started playing league, I thought that AD carry was the place for me. I level from like... 1 - 23 on ashe. Mid just was not my thing, for some reason.
Now I play AP mid for our team, and AD carry is the only role that I can't reliably play. XP

If you're looking to go mid, try xerath. He's my personal favorite because of his long range for easy harass. Land the stun combo and great justice ensues.

Another thing you can try, is playing with other AP mids if you seem to be liking Veigar. Veigar relies heavily on burst combos so a few other burst dps mids you can try are Anivia, Cass, or Leblanc.
As for your shaco jungle, he has really strong ganks because of his decieve and slow from his thrown dagger. You could try other strong gankers like Alistar jungle or you could experiment in low tier games as blitzcrank jungle (not recommended). Just try to get a broad spectrum of all the champs that carry similar attributes for the champions you're playing as now.
Website wise, I always prefer to go to solomid.net because it has a whole page of livestreams from all top tier League players, builds from top tier players and not just random people, and in depth guides on the specific champion. Watching top tier streams for the position you liek to play can greatly improve your gameplay

^ I can agree with that post (except maybe for the viability of Shaco jungling...;P). The absolute best streamer for League is Scarra. No one else even comes close. Check out his stream and videos, its an AWESOME way to learn all the little important things about mid.