Hey there! Congrats on your new betta!! Everything that Sweeda said is spot on! I'm going to go a bit more in depth
Definitely get him a bigger tank! A 1 gallon is a bare minimum in my opinion, and only for people who are experienced in betta care. For you I would suggest 2.5 gallon tank or more. You will need to preform 100% water changes every 3 days or so if you don't get a filter.
If you can't afford a fish tank, you can usually find 2 gallon critter keepers at petco/petsmart/walmart for around $15, they dont have lights but they're a cheaper alternative to an over priced fish tank and work just as well.
You'll want a heater set to between 76-82 degrees F. And dont forget a thermometer so you can keep track of the temp in the tank!
What type of food are you feeding him? I recommend pellets (Hikari betta bio-gold is one of the best, Topfin is also really good), just 5-6 a day, and some bloodworms 2x a week. Its also a good idea to fast your betta one day a week so he doesn't become bloated.
If I think of anything else I'll come back, lol. Good luck!!!! And I would love to see some pictures!!