How exciting! Best of luck and make sure you show us photos when you are done and let us know your final stocking.
I will advise you that the one inch per gallon is not a viable guide. It doesn't take into account length of tank vs. height; the three levels of occupation (bottom, middle and top), substrate, equipment, etc. Footprint, not gallons, determines how one stocks an aquarium. That is how it is done here: AqAdvisor - Intelligent Freshwater Tropical Fish Aquarium Stocking Calculator and Aquarium Tank/Filter Advisor
Shoaling fish need a minimum of six; however, if housed with a predator like a Betta the minimum should be 10 if smaller like the Neons. Neons in small shoals, IME, tend push their aggression outside the shoal onto their tank mates; especially slow-moving long-finned Betta. Plakat Betta not so much.
Make sure there is heavy planting as the Betta will need places to retreat from the others. As I said, Betta are slow-moving and their fins the target of fish in insufficient shoals.
Personally, I have found the Betta in my Betta-based communities do best when the other fish are smaller than they because they *are* slow-moving and easy targets to larger fish (those more than 1"). My best communities have had small Rasbora, dwarf Cory, Neon, Green Neon, Ember Tetra, Endlers Livebearers, Dwarf Panda Guppies, Dario Dario (must be fed live food), Hara Jerdoni, etc. I would look askance as skirted Tetra and those that are 2" or better when grown.