2 gallons isn't too small for a betta. Niether is a one gallon really, as long as you are very good about keeping the water clean and the tank tidy and you have it in a place where the temps aren't fluctuating too much.
I have some very happy healthy betta in 1 gallon tanks. their color is good and they are very lively and active. I do keep them near one another so they have another fish to interact with. They flare at each other a bit when first introduced, but quickly settle down once they get used to the fella next door.
I also have betta in a 5 gallon tank and a 10 gallon divided for 4 betta...both have a filter and heater. I love these fish and take very good care of them. I collect them because I enjoy the many varieties of color and finnage that you find in the betta. I have to chuckle when I read folks getting all incensed and outraged with bettas being in anything smaller than 10 gallons.....but I also think it's a bit much to pile on someone who does have them quite content in smaller tanks....as long as they are keeping the water quality up. Of course, betta most certainly do make a very nice show fish for any larger tank, as long as the tank mates are compatable.
Sorry, enough of my rant, if you want to call it that..........Dixie...check the PH level of your water. I have found that higher PH can effect the health of bettas fins. I had one in perticular that no matter how clean I kept the water....and took EVERYTHING out of the tank thinking he was possibly snagging his fins on the plants....his fins still would tatter for no apparent reason. I put him in a tank with peatmoss underneath a plant substrate...got the PH down to 7.6...(it was 8+ !)...and I haven't had a problem with him since. Also, be very careful about how much water conditioner you add to the water....and do let the water sit for a few days at least before you use it for a change.
When you buy your bettas, make very sure they are healthy and active...with no signs of fin damage or rot. If you find out when the store gets thier bettas in you could go and buy them on that day. Then you know they havn't been sitting there for days and weeks before you buy them. Better chance of getting a healthier betta...and also an unusually colored one. The nicest ones go pretty fast. I totally understand your betta obsession....lol....
Also, carefully and slowly acclimate them to their new home..adding a bit of your water to the water they came in...helps too