You should also try to take more time in painting, and dont stop until it looks as best as it can. clean your paint up. it might be me or the camera quality but i see paint where it shouldnt be. It takes practice and patience and lots of crappily done models (trust me, i did 26 crappy models before i got it.) to pick up tricks that help you do that, you just habve to keep painting, and if buying more models goes against your budget, strip and paint again.
I will add my own agreement to this as well Sink. Nothing will ruin a model like paint on the wrong spot and it is something I have to continually check for myself. You don't have to be an -incredible- painter if you are a clean painter. It makes all the different in the world. Keep at it, make sure you get a nice smooth coat on for each layer and touch up the spills and you will suddenly see vast improvement in your minis.
Oh, one other thing: grey makes for a terrible contrast with most things. Try to avoid it as a main colour and you will be much happier.