You could just start off with an Aqueon Minibow.
And use this http://www.petco.com/shop/searchresu...6238&cmrefpf=1
And buy a thermometer.
If the temperature is too cold, then grab some of the gems and run the over hot water, then drop them in to the tank.
Where I live is extremely hot, but every so often we get cold "storms". They just randomly blow through. When this happens and I notice their tanks are getting kind of chilly, I will remove partial water and slowly add in warmer water.
For example; if I see it's at 74*, I will take out 25%, then slowly (over a course of an hour) add water about 84* or so. Then, by time the tank is full again, the temperature is up to 78*-80* generally. Usually it stays around this. The tank light on mine does warm the water, but only by 1 or 2 degrees. So if the water is about 76* or so I'll usually put the tank light on for a bit so it'll go up by just a tad over some time.
Another great tip is just do frequent water changes. Putting water in at 82* in a 2 gallon with decently warm inside temperature means that by the next day the tank will be down to about 74*-78*. (Depending on how cold it is.) Therefore if you're regularly changing all the water it'll maintain a good temperature. Especially if you slowly get your betta used to the water when you do this!
This is not a permanent situation though. It's just a good one until you can afford one, or until it starts to get cold. (It IS summer, so be careful of your household temp. Because it's hot outside usually people crank up A/Cs or fans making the house/apartment 78* or less, meaning tank water will be at 70*-72*!!!)
Where I live is extremely hot, but every so often we get cold "storms". They just randomly blow through. When this happens and I notice their tanks are getting kind of chilly, I will remove partial water and slowly add in warmer water.
For example; if I see it's at 74*, I will take out 25%, then slowly (over a course of an hour) add water about 84* or so. Then, by time the tank is full again, the temperature is up to 78*-80* generally. Usually it stays around this. The tank light on mine does warm the water, but only by 1 or 2 degrees. So if the water is about 76* or so I'll usually put the tank light on for a bit so it'll go up by just a tad over some time.
Another great tip is just do frequent water changes. Putting water in at 82* in a 2 gallon with decently warm inside temperature means that by the next day the tank will be down to about 74*-78*. (Depending on how cold it is.) Therefore if you're regularly changing all the water it'll maintain a good temperature. Especially if you slowly get your betta used to the water when you do this!
This is not a permanent situation though. It's just a good one until you can afford one, or until it starts to get cold. (It IS summer, so be careful of your household temp. Because it's hot outside usually people crank up A/Cs or fans making the house/apartment 78* or less, meaning tank water will be at 70*-72*!!!)