I like natural colored gravel. It just seems more peaceful. But that may not be the look you're going for, so it's really more personal preference.
Live plants are awesome. Watch out for sharp edges on plastic plants.
I think I must have tried every food under the face of the sun to get my first betta to eat. The only one he ate was Wardley's pellets. My current betta goes crazy over frozen bloodworms and I alternate between Wardley's pellets, Aqueon pellets, and a powder food that was given to me by a betta breeder. I think it all depends on your fish's taste!
Have fun with your new tank and fish!