Breeding anything, not just fish, is best accomplished if you reverse engineer it. Where will 50-100, maybe more young beautiful bettas go to? This should be your first step; their final destination. Try dealing with small independently owned shops, but do understand that when you have fish ready they may not be ready for them. Count on about half backing out. If you have no market don't bother breeding them, unless you are interested in keeping a lot of fish long term.
Next, like anything else, the market will fluctuate. You may have to hang on to the grown and sellable fish for a few months until you find a shop, broker, or buyers for all of them. This means 50-100, maybe more containers suitable for them to live in. This also means an area for them, with proper conditions, as well as your own personal time and money to invest in this. If you can't provide any of this, don't breed them.
If you have the market, and you have the resources, great. One thing you do have to realize is that every fish will not grow up to be perfect. Culling is one of the most, if not the most difficult part of breeding anything You are not doing the aquatics trade, nor your breeding program any favors by keeping or passing on these fish. If you don't have the heart or the stomach for doing this do not breed them.
Small fish require small food, frequently. You will need infusoria, microworms, vinegar eels, and a baby brine shrimp hatchery. This adds to the time and cost. Once again.....
Many species can get aggressive leading up to during and after spawning, bettas are one of those. Actively breeding fish are often not show quality fish. If you can't take some ripping & tearing of fins & scales, other injuries perhaps at times leading to fatalities...
If you can’t work with any of these situations, enjoy your fish for what it is. Breeding fish properly is often exciting, often disappointing, always a learning experience as well as always being more work that you thought it would be.
If you are all good with the above there are knowledgeable breeders on the forum. These are some of the things that are rarely, if ever covered. Conditioning breeders, spawning triggers & behavior, the spawning event, and hatching schedule with the male present or without are often dealt with.