Basically, what I've found over the years, that there is a vast difference in the quality of players, in accordance with the level of buy-in.
Firstly, if you're used to playing freerolls, and want to jump in to buy-ins, you will find a heck of a lot of difference in the style of play. Anything over $5.50, and you will find that these players are much more serious, and not as free wheeling.
Anything that's $5.50, and over, you just cannot play the same way.
For me, I've found that anything over $11.00 starts to get really tough, because you are getting into serious $$$, and they play very, VERY, differently. If you're not patient, and want to be free wheeling, they will eat you alive.
Here's a suggestion: Take an observer position at a game above $20.00, and you'll see what I mean. There is a lot of folding going on, right from the beginning.
If you can play like that, without letting impatience get a hold of you, you might do ok.
I'm very patient, but at these levels, these players really know their stuff, and they are tuff.
I'll usually stay at $11.00, or lower.
Don't know if that helps, but it's what I've found works for me.
Good luch.