In the beginning I bought everything because...well, I had to see and feel them out (growth-wise) for myself and dive right in because that's just how I pick things up.
Now I'm slowly thinking about trading away the ones I don't absolutely love and that don't grow so well for me. I poured a bunch of money into buying my plants and spent money on little else, which didn't really hurt me at all (other than not building up a bigger savings...oh well) but did help the businesses I purchased from. And made me happy of course. I did keep in mind that I planned on paying off my credit card in full each month, and though sometimes hard, I am sticking to it. And most plants are between $5-$15 anyway, if you buy them small, which is what I usually do (is why my plants are all small). It'll help you appreciate them more if you work on growing them from baby-sized anyway