You will need:
- a 5-10 gallon tank. Not a bowl! Bowls are super bad for bettas. They can't be heated or filtered, are way too small and don't have lids. You often see tiny tanks marketed for bettas, but no betta can be healthy or long-lived in such a home.
- A heater and thermometer. The water should stay between 78 and 82 F for maximum betta health ,activity and colour. They are high-end tropical fish, so people suggesting that room temperature is enough is ridiculous.
- A gentle filter. Sponge filters are ideal. Because bettas are poor swimmers, they can't cope with really violent filters, but they still need at least some filtration. Sponges are great.
- Water conditioner. Prime is the best out there, but AmQuel is pretty good too.
- A liquid test kit. The API master kit is really good.
As for decor and such, what would you like? Do you have a colour theme? For instance, red bettas look great against blue, so you could get a blue background, blue gravel and red and blue silk plants (not plastic, these can tear his fins).
Another alternative is the natural look. Some small gravel, a few polished river stones and some cheap and easy live plants like java fern make a nice touch.
A zen tank also looks really nice. White sand with some natural, black or white river stones, a buddah statue, some java moss and some plants in sake cups are really nice. Lacefern and ambulia are both easy to care for and look great in zen tanks. So does java fern.
Red cherry shrimp would makea gorgeous addition to all of these tanks.
Before you buy your betta, make sure you cycle the tank. It's a long, boring process, yes, but it is so important for the health of the fish and will make a massive difference. Also, it gives you time to plan and decorate the tank in minute detail and get it just how you want it.

http://aqadvisor.com/articles/Cycling.php This link should explain more if you are not familiar with the cycle.
I hope this helps and that you can make the exact tank you want.
