Congrats on you new fish! He's gorgeous!
Well, feeding him once a day is ok, it's better to less quantity and 2 or 3 times a day but if your schedule doesn't allow it, that's fine.
Are you feeding freeze dried or fresh? If you're feeding freeze dried, you should add something else to his diet as Freeze dried worms have very little nutrition.
What size tank do you have him in? Do you have a heater? What's your water temp? How are you treating the water? What is your water change schedule?
Lot's of Q's, I know but a lot goes on in betta keeping