Things you can do to speed up your cycle:
-Get filter media, substrate (gravel/sand), decorations, live AQUATIC plants, from established tanks. If you have a friend who has a tank get some, ask for some from your LFS, if the betta's came from those small bowls and you still have them, AND they have been kept wet you can rinse them out with tank water and put them in the tank (they have bacteria on the insides).
-Feed VERY sparingly, once a day max, better yet, every other day. Anything they don't eat in a couple minutes get it out of the tank. Any visible fish waste or food on the ground should be removed. Very light gravel vac if you have one or manual removal with any method you have is fine (turkey baster?)
-Do frequent PWC's. I'd do 50% per day until you get a test kit (liquid test kit). After that you can use the test kit to decide when a PWC is needed. I can guarantee after a week of 50% PWC in each tank you will somehow be able to find the money for one.
Things you should NOT do:
-Don't overfeed (#1 way you can harm your betta)
-Don't neglect the PWC's
-Don't add any ammonia absorbing chemicals, this is a quick fix that can harm the bacteria and slow/stop your cycle, just keep up with the PWC's every day
-Don't add any other chemicals. ZIP, ZILCH, NADDA. Anything the LFS might have made you buy return it. This means pH adjusters, water treatments (other than a dechlorinator), medications, and fizz tabs. LFS' LOVE to get a lot of money out of people new to the hobby, and the majority of these are NEVER needed. If you have some of these and can return them, you just got a liquid reagent test kit for free....
-Don't add in straight tap water. Make sure the water you are adding after a PWC is the
SAME temperature and has been dechlorinated with a product such as Prime BEFORE adding to the tank.
Good Luck.