I would get a 2-10 gallon tank, Kritter Keepers do work well. As well as a heater appropriate for the size, and an air pump with an air stone is always a good idea. Get a couple SILK plants (sold at pretty much any pet store), as they will not shred the fish's fins. Get a thermometer, too.
Omega One is a good food, I use it, & also flakes & frozen foods are good supplements. In Summer (or if you live in a warmer climate), if you set out a pan of water, after a few weeks mosquitoes will lay eggs in the DIRTY water (it needs to get dirty, or else they won't lay). When these mature, they make a great food supplement. Rinse with tank water before feeding.
Hope this helps! I hope your Betta gets better!!!!! (Have you named him? ;) )
Some useful links!
I use this one ^, but it keeps the water somewhat cold in my 3 gal. :/