I agree that there is a lot of debate around betta tank size. My personal opinion is that you should look into at least 5 gallons. Other than that, if you don't you will need to take more care of the tank than you would otherwise or your fish's health may suffer. Bettas insist on survival but that does not mean they're healthy. If you do get a tank smaller than 5g, please do some good research on how best to handle it.
Back to your initial question though, walmart does have a <$30 startup kit tank here:
https://www.walmart.com/ip/Aqua-Culture-5-Gallon-Fish-Tank-LED-Aquarium-Starter-Kit/20693704
It was recommended to me by others on this site, and I would have gotten it if I hadn't opted for a 10 gallon. Plus, it's a little cheaper than buying the parts individually. I wish you good luck!