UPDATE:
I ordered some plants from Marcus Fish Tanks. If you haven't seen them, go check them out. They sell nice, big, healthy plants and ship for $5 for 1-3 day shipping.
@black_cat do you want me to provide you with a list of everything you will need? IDK if that helps you, but it helps me a lot to have a list of what I need.
Then I would recommend some full spectrum lighting.
https://www.amazon.com/Hygger-Spectrum-Extendable-Controller-Freshwater/dp/B07X9T9PV6
Here is a video on where to get bettas.
Depends. Are you going to have live plants? NOTE: Live plants are very easy to care for and provide a TON of benefits for your fish. I could recommend a light and some plants if you want.
I think agree would be very useful to. If you had to add one, that would be the one I want most. Lol if someone feels the same way, they could use the agree reaction to react to this post.
@black_cat I would suggest you get a Halfmoon Plakat (HMPK) betta since they don't have the fin problems that the longfin ones have. They are less prone to fin rot and can swim properly. Plus, they come in very cool colors such as Koi HMPK.