New betta parents, question about tank upgrades!

Hey everyone!

My wife and I wanted to get fish and after some long discussion we decided on getting a betta, we got a platinum and named him Blizzard.

After some brief further research after getting him we learned that plants are basically mandatory for them, so we got him one. But having seen everyone's beautiful tanks here, I realized we need more.

So when it comes to tanks, how is the best way to add more to his tank and also be sure not to stress him out. I know I also need to add in a few hiding nooks and those are on the list as well.

Any other advice appreciated. We always get sad seeing them in little soup containers at the stores and want to give this little guy the best life possible. He's been so active and cheerful, and has such a big personality. He loves flaring up at me when I come visit at night to feed him and essentially tuck him in.

5.5 gal, heater and pump + filter.