By the way, if your common guppies were feeders. I would quarantine them 2-4 weeks before keeping them with any other fish. "Feeder" tanks are also notorious for being museums of fish diseases and parasites. I would also treat them for internal parasites while they are in quarantine. Otherwise, as much as three months later, you may be in for some nasty surprises. :(

It is possible to develop a fancy strain by crossing a fancy to a regular guppy. However it will take you a couple of years to even a decade to sort out and select the offspring. That is just my guess, but it would be quite a few generations, with separate tanks for virgin females, separate tanks for fry and a faithfully kept stud chart.

Sometimes a fancy guppy breeder will introduce another fancy line into his. He or she may select for size first, then finage and then color. It may still take a few generations to get what they like.

Usually breeders of fancies, which by the way are much more touchy about water quality, temperature changes and crowding than common guppies (the fancy guppies that is, not the people keeping them), will keep maybe three lines of each strain, breeding them to others within each of the three (or four lines( and then every four or five generations, the best from each line will be crossed to the others. For a line, one might need 6 to a dozen tanks; for the three lines, one could conceivably tie up 25-30 5.5 and 10-gallon tanks. For more on this Google Guppylog and the web on "Linebreeding Guppies".

I have mellowed about just crossing stuff from pet shops to see what will grow up. It is interesting and even amazing what gets dropped! Indeed, shops often combine guppies of different strains as their numbers decline (hopefully from sales). This means that each female will probably have been "hit" by an average of three males and the males might have quite different heritages. It does take a lot of effort getting mixed lines to breed consistently.

For really reliable strains, I would encourage guppy people to look for someone from a local fish or guppy club. Guppy shows will also have auctions - look for youngsters of strains and  in the show. Look to see that the guppies in the bag are raised by the same people associated with the show guppies you liked. I would not buy big breeders. They are probably show fish, pretty much done with showing and likely to die within a month or three.

The IFGA site has a store, see http://www.ifga.org/
The IFGA recognized strains are fewer in number that those offered by a number of web sites. I know that there are some terrific images of guppies that I too would like to try. Be careful of fanciful names. Sometimes those are just advertising. (There are a number of names sometimes for what is essentially the same fish.)
Certainly Aquabid can be useful. Make sure your seller has a good reputation. I'd also look for someone pretty near your home in that shipping may be less stressful and water chemistry "may" be similar.

If you work through a local LFS (Live Fish Store), which has proved itself pretty reliable, you might ask them if they could order a batch of fancy guppies you have encountered on-line or in the books. To make it worth their while and worth their while to keep those fish by themselves for a time, promise to and do buy two or three pairs of them.

Later tonight or tomorrow I hope to put up a list (hardly comprehensive) of web sites, which show some of the different types of guppies in the hobby. That is part of a response to "Different types of guppies" by kitty got claws18.

As time (that most precious commodity) permits, I would encourage a curious and thoughtful person like yourself to pursue as many reading opportunities as possible. There are a lot of web sites with good info on guppies. I have encountered some disturbingly mistaken comments about guppies from some general aquarium forums and even a couple of modest sites dedicated to guppies. So test everyone's comments - including those at Guppylog.

Heck, we haven't been wrong in a couple of days. ;)

Reading opportunities might include our own Immediate Help. There are also a few book recommendations and lists floating around on GL. One could pretty easily trash their budget just buying guppy and aquarium related books. But copy down or print references that sound good and drop by your local public library. Through your taxes (sales, property, state income...) you have already paid for their Inter-Library Loan Service. I am absolutely delighted with what some reference librarians have done to conjure up books from places I would never think to look in (or spend $50 in gas to get to.)

(From Immediate Help) http://www.guppylog.com/story/2005/12/6/93245/5791

Here are questions raised recently, which may throw a little more light on your question: http://www.guppylog.com/?op=displaystory;sid=2008/7/21/19623/5822

http://www.guppylog.com/story/2007/1/12/62743/3985

http://www.guppylog.com/story/2008/1/9/18258/82382

The guppy book I would most recommend to you at this stage of the game would be Stan Shubel's Aquarium Care of Fancy Guppies (Hardcover, 2006. TFH Press) in a new entry, listing at $9.95. It seems to be in the big box book stores around here. And they replaced it when I bought a copy. ;) If times are a little tough, bring something to take notes on and with, buy a regular coffee and camp out with that book. ;)