Three years is long! Anyways, welcome to the forums!
First off, you want a Betta? These are the things you'll need:
- A tank, somewhere around two to five gallons, bigger is always better.
- Heater is a must, I recommend the Elite brand.
- Filter, it's not a must but it'll be much easier for you.
- Food, a variety of them. Pellets, flakes, freeze dried, and frozen.
- Water conditioner!
- Lighting, they'll often come with the tank.
- Decorations, be sure it's fish friendly.
- Gravel/sand, basically a substrate.
- Live plants (which is quite costly)
I think that's pretty much it, don't hesitate to ask more questions!