Bristlenose plecos are neat and easy and the babies will sell, not for much but always. They start with about 25 fry and in a few years it will be closer too 100 a spawn
In most cases for breeding you normally need a minimum of two tanks per species. One for spawning and one for growout. As you have more species you will find keeping a spare tank or two ready to go is a must.
Consider when you pick what to spawn how many fry you might get. A spawning pair of angels in a 25 or 29 gal tank usually requires a couple of 55 gal. grow out tanks. A pair of small hypancistrus plecos may give 15 or 20 fry.
Spawn what interests you. Spawn what you would like to see spawn. There are pair spawners, group spawners, egg scatterers, substrate spawners, stick eggs to something spawners, live bearers, mouth brooders, bubble nest spawners, cave spawners. The splash tetra leaps from the water and spawns on an over hanging leaf and then splashes it to keep the eggs wet for a few days.