Playing with fun money will get you used to the interface, but that's all. It is pointless trying to learn how to play poker by playing with fun money. The standard of play is so bad.
Try playing a free roll (a tournament with no entry fee, and small cash prizes. Often thousands enter, you might win $50 at best, on the very good sites; more likely $1-$10. But at least it's real poker.
I just won $100 in two tourneys, but I'm furious at myself for losing all my money and going out 5th, when I had the third highest chip stack and was starting to get back into the game.