Baby shampoo is really a pretty good one for a dog if you don't need a flea shampoo, and you can use a little creme rinse afterward. It primarily makes sure all the soap residue is gone.
Give her a bath when she stinks, man! You shouldn't have to bathe her very often. Even if she gets out and gets muddy, just rinse her off; save the hardcore bath for times that she just stinks or she's scratching more than occasionally.