Many breeders spawn in 2.5 gallon tanks but you will need to transfer the fry to a larger tank once they're about a week old. I prefer to spawn in either a 5 or 10 gallon because the fish can stay in there longer.
To be honest it doesn't' sound like you're ready yet. You'll need heaters for every tank, plants, live foods, jars, and lots of space for all the babies. Depending on the size of the spawn you probably could spawn and grow out in the 10 gallon but if you get a spawn with a large number of females it wouldn't be practical to keep them in such a small tank.
I would check out craigslist and thrift stores and look for cheap tanks that can be used for grow outs. I was able to pick up a 55 gallon tank for $35 which would make an excellent grow out tank (if I had the space to set it up LOL).
While there are many different ways to breed, I think beginners should stick to the most popular method and then tweak from there. That would be a 10 gallon filled 3-5 inches and heated to 82*F, female in a jar before being released.
Once the males become distinguishable you can keep them in 0.5 gallon jars but remember that the smaller the jar the more frequent the water changes you'll have to do.
As far as your pair. I would start out with a nice sibling pair whose colors and finnage are what you would like to see in your off spring. While starter pairs can get pricey at time it's far better to start out with quality genetics than to try to weed out all the problems of badly bred fish.
I hope this helps a little
Welcome to the forum and if you have any more questions feel free to ask
I'm always around.