Welcome Emmett, somehow I missed welcoming you to the forum .... at my age I tend to miss some days too, but that's another story! It sounds like you've got a pretty good start, I like Guppies for a small system, as Goldies require more water volume per fish (according to those on the Goldie forums), those folks thought I was terrible when I told them that I was going to eat the fish when they got large enough!

Guppies are hard to kill, and tend to reproduce quickly and often, so I would get 3 or 4 fancy males and about twice as many feeder females, and let them go at it! You can possibly sell the male offspring for 30 to 50 cents each to local pet shops as they get old enough to identify, to help defray some of your costs if you live in or near a large city, and when you get your Tilapia tank going, you can feed any extras to the Tilapia ... they go crazy for them!