For some good information about how to sell your geckos, check out this article titled, appropriately, "How to Sell Your Geckos":
How to Sell Your Geckos | Gecko Time
You can certainly post on the classifieds here --it's pretty much free and easy. There are a lot of leopard geckos for sale on these classifieds, many of them by people who already have a reputation. Also, this is an international forum. You will likely do better locally.
The question of what to breed your Bell with really depends on what you think of as a nice looking gecko and what you're hoping to produce.
Aliza
