Your Betta is such a beauty! I love my 72G bowfront. It has changed so many times in the years I have had it.
My suggestions are trying an Anubias nana, nana petite or my other favorite, Anubias Coffeefolia. Do not bury the roots. The long stem part the leaves attach to is the rhizome and burying it leads to it rotting. Low light is fine, away from the brightest light or near the bottom. Very easy.
Then just start on a couple more, which I would suggest a Java Fern, common is fine but the narrow leaf is really attractive. Also attach to DW stone or wedge into a corner with some stones. This one is also not planted in the substrate.
Before I had all live plants, I just stuck one of these into the branches of a fake plant like a kinda green pom pom accent.
Crypt Balansae Crispus ( gets long or Cryptocoryne Lutea or Crypt wendtii (several color variations) bronze green red are all easy.