Hey there Abasith!
I'm working on a blog post about this as we speak! However, for now:
I ALWAYS recommend buying two sets. One that's a pretty nice, durable set and the other one a cheaper practice set. Below are the two I recommend.
My personal favorite performance cups are the Penguin Cups (and not just because I work here!). They're priced reasonably and they're VERY high quality cups. The mouth load is a good size for most final loads in routines, and they're DURABLE. I can't tell you how many times that I've dropped mine and they still look just fine. If you take care of them, they'll last you a lifetime.http://www.penguinmagic.com/p/742
As for another set, I recommend the Wooden Uday cups. It's almost impossible to break or scuff them, so they make an ideal set when learning and practicing the moves. http://www.penguinmagic.com/p/2032
That's why I buy two sets: whenever I'm learning a new move or practicing a new routine, I use my wooden ones. Then when I get booked for a show, I pull out my Penguin Cups. The Penguin Cups can take a beating, but they'll last so much longer if you don't use them for practice. Plus, the cost of both of those sets is less than one set of some more expensive cups.
As far as learning resources go, Michael Ammar's DVDs are good, Gazzo's DVD is good... but my favorite cups and balls routine of all time is David Regal's. On volume 2 of David's Tricks DVD set, you get to learn an absolutely INCREDIBLE routine with cups and balls, but more importantly, you'll learn many of the standard moves (definitely enough to create your own routine with).
Hope that helps!