Gorgeous fish! Welcome to both of you!
Also, lots of plants will help keep your water super clean, and the best plants for a gravel-based tank are things like java ferns, java moss, moss balls, and floating plants if you like those. Some people put "lucky bamboo" (which isn't really bamboo but whatever) in the tank with the top sticking in the air (don't submerge it totally or it'll rot). That's another good plant. None of those need special light, fertilizers, or substrate. Don't buy plants without researching them--you can waste a lot of money if you don't know what you're getting.
Make sure you have these basic things:
1. Water conditioner. Prime's the best recommended around here.
2. GOOD betta food. If more than one of the first three ingredients involves wheat, it's probably not that great. Omega One pellets and New Life Spectrum are awesome brands of food. Aqueon pellets are so-so. Hikari pellets are... blech.
3. Aquarium salt AND Epsom salt. They're different things, and chances are you'll need one or both eventually (and when you do, the sooner you have them the better). You can use these to treat fish that are just getting sick and help prevent them needing medicine.
4. Plenty of cover for your fish. If you can see him easily every time you look at the tank, there isn't enough cover. Small terracotta pots are a favorite, and can be bought cheaply. I'm partial to live plants like the ones I mentioned above. There's a whole section of this forum dedicated to habitats and accessories to keep your fish happy, including numerous DIY projects, so check it out!
5. He's in a tank that's at least a gallon and a half, right? With a heater? And a thermometer?