My comments go in a different direction. I don't know the specifics of your situation (and don't really want to know much more), however, I feel strongly that any species, when healthy, good-looking specimens are produced by a breeder who takes the time to build up his/her reputation, can be a success for the breeder. It will not necessarily make the breeder a lot of money. I don't think, though, that there is a "magic species" that will make a breeder rich, or that if one thing doesn't work out, the breeder has ruined his/her chances.
By way of example, I regularly vend at shows with my "gecko partner", Matt (SelectGex on the forum here and the other Gecko Time editor). We have an overlap of species we both breed and often are selling very similar geckos at the same table. We check with each other to make sure there's no blatant conflict with our prices. Matt also produces and sells more species of rare and more expensive geckos than I do. We're both selling and both successful. I guess my point is for you to choose what you like and want to work with, produce the best geckos you can build up your reputation and go from there.