I tried this a while ago before I even saw your post - it's really fun to train bettas! i taught mine how to eat from my hand, go through a small plastic hoop that I made, and jump for food. The first and last are definitely pretty simple - I'll explain how I did the second one with my old betta Chauncey.
I first taught him to eat from my hand (underwater, of course!) and then I introduced the hoop. When he swam toward it, I rewarded him with food. Next I placed the hoop in the tank and held the food on the other side. With enough encouraging, he saw the food and swam through the hoop to get it!
Bettas are really smart!