Well price and your taste in fish is your personal preference so I can't say much there.
I see in your signature that you already have cherry barbs in a 40B, maybe you wouldn't mind not getting more cherries for this tank to "save" a bit to put toward the other fish?
By the way, probably best to get some fish at a time rather than all at once so you don't overwhelm the beneficial bacteria and cause an ammonia spike with the sudden large increase in fish bioload. You might save up some money in that time as well.
Do not split the schooling fish into 2 or 3 species. This is a smaller tank, so just select one species of Tetra, and get a dozen.
Cherry Barbs are not so much schooling as social. You could get 2M + 3-4F and see how they get along. Sometimes the males are somewhat pushy.
Melanotaenia praecox males can be quite pushy toward the females, and can stress them to death. I would go with a smaller rainbow, but not the dwarf neon.
M. maccullochi is a nice one. Melanotaenia maccullochi