If you simply want to breed your one best male to some females, I would encourage you to go for it. In order to actually get the results that you want, you will need to remove any competing males and make sure that the females you use come from the same line of guppies.
Most pet shop guppies come from poorly selected fish populations and that is why each fish is unique in its appearance. Unfortunately that means that it will be hard to establish a line of fish with similar characteristics because the genetics of the parent generation will be such a mix of characteristics. By the time you can separate out the wrong fry from your population, it would have been cheaper and easier to start with a well bred parent population. A "good" guppy adult from a private breeder can easily demand many times the price of a pet shop variety but it will give you a huge head start on getting exactly what you want in the fry.
As far as numbers of fish are concerned, a small tank like a biube makes line breeding far more difficult because you will need to constantly remove most of the fry. For effective line breeding of fish, it takes multiple tanks and good sized ones to grow out each sex of each individual drop of fry. Most of the hobbyists here, even me with my 26 tanks, are not equipped for such an endeavor.
