Great idea, I've started keeping a running log of whenever my guppy's breed, mainly because I've decided, as well, to take that more seriously. Now, there's a few things about it that I think personally.
Of course, the majority of the "fancy" and "feeder" guppies that you get will have been bred to be this way for generations (that case more apparent in fancies) and feeders seem that they're just the needed part of the fry that should be culled. I've had a fancy guppy male and female breed, and the offspring were, in turn fancy but there were fry that were not as pretty and ultimately I had culled.
On the other hand, that same father (a fancy red guppy to be exact) bred with a much more plain guppy (some light yellow on the tail but otherwise no coloration) and this has produced fry that actually include males (first batch all female [that is, the batch from fancy red male and fancy leapord female]). Also, the Fry between the Fancy red and 'feeder' female has produced a beautiful freak baby boy, that has gotten color much sooner than the other fry did.
My first batch of fry took about 4-5 months to start developing color, and this freak baby took less than 2 months, actually born with color. Since then, The fancy red guppy boy has bred with a third female (tequila sunrise female) and I'm awaiting those results. What I have found that even those feeder female guppies are capable of birthing beautiful offspring and fancy females are capable of birthing dull fry and beautiful fry.
The best option you will have will ultimately be to acquire your male and females from different stores to reduce the risk of having an inbred group (optimum ratio 1m-3f), as many fancy guppies are line bred to enhance that trait and we all know what inbreeding can ultimately lead to. Honestly, I would go with (tanks willing) two males-one male fancy and one male feeder, and mixed female fancies and feeders so you could see all possibilities. If you don't want/have the necessary room/tank space, i'd say go fancy male and feeder female.
Best of luck with you, this will be fun to follow along with.
Never in the field of human conflict has so much been by so many to so few- Winston Churchill. "Give a person a fish, they'll be happy for a while. Teach them to breed 'em, they'll be happy forever" -Me