i am on a tight budget just like you, so what i have done is get one rock per pay check. here in japan, at my LFS, the rocks are 2800 yen a piece, which is equal to about $25. sometimes i pick a bigger rock that doesn't have a lot of growth on it, and sometimes i pick a smaller one that has a ton of stuff on it. so far, i've got 5 different rocks in the tank and i am actually getting pretty happy with the way it looks. i know with the budget thing, it helps to do a little at a time. HTH