Buying happens the first time you acquire art. 
Collecting is what happens AFTER that.

Some strategies to try out:

- Think about collecting around a theme, such as subject, medium, or period. Make a goal to collect four works --maybe animals or landscapes-- each done in a distinctly DIFFERENT style or medium, by a variety of artists. (Do not become the weird guy with 20 seascapes all done in impressionist watercolor by a single artist.)

- Collect from a particular period. Often you can find affordable drawings or studies even by BIG name artists. If you like history, this is a really nice way to tie together history and art, especially when you travel.

- Collect sculpture that is kinetic, or sculpture made entirely of one medium such as metal, or sculpture made for outdoors, or made to hang on a wall. 

Collecting is an excellent way to hone your "seeing" skills, because you become very FOCUSED. By looking intently for one thing, you actually begin to see other things. You begin to appreciate other art forms, styles, mediums... You begin to see like SUPERMAN.
You develop more gut instinct that you can TRUST.
"Superman" by Andy Warhol