Don't bother bathing your pet till he is 3 months old. Brush him regularly (everyday if possible). If he gets too dirtly, just wipe him down with a cloth dipped in luke warm water. You could add savalon to the water, but savalon is not good for your puppies skin. So avoid savalon too, if possible.
After he is 3 months old, once in 2 or 3 weeks is MORE than sufficient. But, you need to ensure a clean coat. So do not underestimate the need to brush him as regularly as possible. Brushing him can also be a good opportunity to bond with your doggie. I tell my doggie fairy tales when I brush her and sometimes all the things that happened to me during the day. She just loves the interaction with me and hearing my voice, I love the soothing act of brushing her and talking out aloud all my worries. Try it :)