I was already a confirmed "plant-o-phile" when a Christmas gift from my sister got me interested in bonsai. I too went thru the stage of buying left and right, not really knowing what to look for -- but enjoying myself anyway!
Gradually I began to realize that not everything that caught my eye would make a decent bonsai. I also realized that I was spending so much time simply keeping my trees alive that I had no time to enjoy them! That's when I began to cull, and to concentrate on the better ones, both among what I already had, and in new purchases. What helped refine my eye the most was reading David DeGroot's book
Basic Bonsai Design. The book is excellent, and I recommend it to anyone, novice to advanced.
At one time I had over 200 intended-for-bonsai plants. Now I'm down to about 40 that are either already part of my permanent collection or will probably end up there. I won't gripe too much if that number gets winnowed a bit more in the next few years.
In addition, I have another dozen or so that "deserve to be bonsai," but that I don't intend to keep permanently. Trees like that I grow on, style (at least partway,) then sell or give away. One place where small trees are often welcome, I've found, is in school classrooms.
Libby, like you I'm one of those who can't stand to discard trimmings when they could be rooted!
Most of those plants end up on the sale table at our club shows in May and October.