Good luck to Phoenix, but what Alex said, we don't know what temperature that lamp is making the tank either. You need a thermometer to really tell.
IN MY OPINION, bare minimum supplies:
1. 2.5 gallon tank, preferably with a hood to keep them from jumping out. Actually, check this out: http://www.petsmart.com/product/inde...ductId=3611436
OR, since you're paying almost as much for this one as you would for something bigger...
Two ideal tanks. Filter, hood, light bulb. The only thing its missing is gravel, silk or live plants, and a heater...
25 Watts for 2-5 gallons, 50 Watts for 5 gallons to a certain point.
And then just a glass thermometer.
3. Water conditioner. Prime by Seachem.
4. Food of some sort. I like Atison's Betta Food, purchasable off of www.lnt.com
. I also feed freeze-dried bloodworms once a week.
These are the BARE MINIMUMS. If you want to go even further with your little hobby at this point, you could get a freshwater testing kit and even get some live plants for your tank. With the 5gallon tank live plants are amazing. <3 But that is for a different time. Post in the Betta Fish Care forum if you want more suggestions. :p