Limit for me to play or stick to NL?

I'm a college student that decided to give online poker a try. I bought in for 20 bucks and turned that into 140 playing 25/50 cent NL. I know it's not much but I was happy with it. I cashed out my 120 and kept the 20, which I've turned into 220 now. Is it time for me to move up limits? I've been playing for seven years and read several books but I feel nervous about playing larger blinds, though I'd like to make more money, I invested a lot of time in making this small amount of money since I'm a relatively tight player.

Is tournaments the way to go? Limit? NL still?

Advice is definitely welcome.