I'm also setting up a 10G betta tank!
I'm taking the opportunity to be a bit bold, though and am doing soil capped with pond pebbles.
For hardscape, avoid anything that is likely to tear fins. So no dragon stone, no lava rock. I'm going with soft woods and a couple of petrified wood accent pieces.
For plants, they love a heavy planted tank and the lower flow they prefer makes them ideal for floating plants like frogbit and water lettuce (make sure it's legal in your state).
I'm going with java fern propagated from my other tank, pennywort, anacharis and echinodorus parviflorus. I've seen people use marimo balls and java moss as well.
As mentioned, stay away from heavy flow filters. There are a lot of HOB filters where you can adjust the output or cushion the flow with sponges. I find this preferable to air pump fed sponges for bettas. Just make sure your intake has a sponge cover and that you can turn down the flow. Bettas are weak swimmers and can get stuck on strong intake or have their fins torn.
Also make sure you have a reliable heater that doesn't have any sharp edges or dangerous holes. Betta can be very curious and can get stuck in plastic parts. But they really need a tank maintained at temps between 78-82.
This also may sound weird, but make sure your betta tank isn't near any reflective surfaces. Bettas, especially males, are highly territorial and will see their reflection as an intruder. They will be constantly stressed by the stranger they can't chase off!