Tank is looking good! If you don't mind a suggestion, Betta are fish which prefer cover and shade as opposed to open water. If you can find a nice wide-leaved plant that would give him the shade he needs. The more plants the better for these critters.
Are you fishless cycling the tank using pure Ammonia or some other Ammonia source? If not, just letting it run won't make it safe for your future Betta.
On the other hand, you can get your Betta and do fish-in cycling. But you'll need SeaChem Prime as your conditioner and an API Freshwater Test Kit. I've found Chewy, eBay and Amazon to have the best prices. Here's the tutorial CYCLING: the two-sentence tutorial
Despite what some may aver, fish-in cycling is perfectly safe. But as with anything else, you must do it properly. I, for instance, have only ever done fish-in cycling and never killed or harmed a fish.
Almost forgot: Check the inside of his Cichlid cave to make sure it's smooth around the edges. I like them but have had a couple that had burrs that would have snagged my Betta's fins.
I might buy some more plants and I'm going to buy a moss ball too.
I filled the water and added betta water conditioner. I was just told to wait a couple days and they'll test my water.
And thanks, I'm going to double check the cave