That would be a lovely planted tank for a betta.
I have that tank in the 2.5 gallon.Don't use the incandescent light that comes with it though..It gets way too hot and I have read reviews about the light that comes with it melting the hood. florescent is better for live plants.
Something like this should work for plants..
I almost picked up that tank in the 5 gallon but it was out of my price range.. I ended up getting a 5 gallon glass kit for pretty cheap at walmart though..it was around 27.00 dollars in store.
Some of my favorite low maintenance plants are java moss attached to rocks, anubias, java fern, anacharis and wisteria. I hear marimo moss balls are very easy to take care of as well, they just need to be rolled around every now and then.