I have always bought art because I like it, that way I get to enjoy it, and if it makes money then it is a bonus.
To find the art that I like I go to small galleries and to art school exhibitions. Art schools are usually a good way to go, but they can be a bit pretentious thinking that they should be paid a lot because they are artists. A bit of bargaining can be good. Another good place to go, if you only want nice pics and are not generally interested in the artists background, try exhibitions of local amateur artists. Again, they can be good sources of cheap, pleasant art, with the added attraction that the artist is often flattered that you want to buy, and, if you are into a more realistic style of art, you are likely to get some good local scenes. I did this with two pics, got the pair for about £70, now they both are valued at £600 each, the artist has become known and collectable. So good pics, bought cheaply, and good investment.