What does it take to beat a game? (or move up)

[pfkaok]

I know that people say 20-30 buyins should usually be enough if you're a winning player, so does it work the other way too? Like if I'm up 30 buyins can I be fairly confident that I'm beating the game? I've only been playing Party's NL $50 consistantly for a few weeks. I feel like I'm definately beating the game, up a little over $1500 after just over 40 hours of playing 3-4 tables... I know that my win rate isn't too impressive, but since I've won over 30 buyins I feel like it probably means I can beat that game. I'm just wondering if somebody who's played both $50 and $100 NL at Party could tell me how easily you should be able to beat the $50 game to feel confident moving up to $100?? And just in general how many buyins you should be up before you know that you're "beating" the game?