"My current idea:
5 Female Bettas
10 Neon Tetras
Some other fish that interest me:
Black Skirt Tetras
It is very good news you are planning out your community tank!
Start like you did with which would be your #1 or #2 favorite fish to have in a tank.
Then build the tank around the fish which would be most important to you to keep. With a few considerations as well.
Not all fish like busy / fast moving fish with them...Example a male Betta would not appreciate the company of busy Danios or Rainbow fish.
A single Angelfish might work fine with some larger fish companions like Harlequin Rasboras, ultimately they can become large enough to eat Neons (which I couldn't believe would happen until I saw it in my own tank.)
Some fish prefer softer or harder water, or different temperatures. Or are nippy on longer fin fish.
Using AQAdvisor.com (usually) works well to alert you of big problems like temps or Angels eating Neons, or fish which need to be in groups, etc. It tends to be a bit conservative. Getting a better or larger functioning GPH
filter can also help with stocking levels.
In addition, if you plan a bigger tank later, often it would be better to get the larger group of - let's say Neons (check out Green Neons too) then when getting the bigger tank do the additional group of new community fish like Von Rio Tetras.
Start with 6-8 Cories, then increase the bottom feeders to something different like 10-12 Kuhli Loaches... All fish listed are just some options as examples.
Also just so you know you can do Dwarf Cories like Pygmaeus / Pygmy Cories which are very small and you can get, say, nearly 2x as many, making a fantastic group, which are much more interesting and active with a larger number, acting more comfortable with many friends.
One last thing to consider, is what the fish will look like when they are together inside the aquarium.
The shape of fish...Glowlight, Neons and Rummy nose Tetras all have torpedo shaped bodies, all fish with the same shape, make the tank less interesting.
Then also consider where the fish hang out,
at the surface like Hatchet fish,
upper level like Neon Green Kubotai - Neon Green Rasbora, Microdevario Kubotai hang out near the top area of the tank
above mid tank Harlequin Rasboras
Neon Tetras mid tank
Corydoras and Kuhlis, Clown Pleco, bottom.
The article in my signature is really useful for beginners and people who are often newer, or getting back into the hobby from awhile back, check it out!