This is just me and what I would do based upon experience. If money is tight, I would forget the Master Test Kit and just purchase another 2.5 gallon tank for Betta Number 2. A Master Test Kit and a 2.5 Gallon tank are roughly about the same price...You can decorate later if you can't afford substrate, plants, caves, etc. But, I would purchase a heater, as well. Do water changes 2-3 times a week for each tank. Eventually, you will want to get a Master Test Kit. This is my opinion only and what I would do if money was tight and I had two Bettas to take care of. I wanted to tell you this as another possible option.