Hi,
In the past, I just ordered mine off e-bay as I need them. I didn't buy a "set".
There will be different tools for different jobs. For example if you are doing v-carving, you'll need roughing bits like 1/4 inch end mill, and finish bits like v-groove tools or ball end mills. These will have different profiles depending on how fine the resolution you are working with.
The finish bits may end up being 1/8th inch diameter, so you might need to get a collet adapter.
You might start looking here:
http://www.rockler.com/power-tool-accessories/router-bitsJeff