If you get a 10 gallon kit from Petsmart or Petco, it will pretty much come with minimal equipment, not the best available but good enough. If you are worried about a place to put a 10 gallon, I have a 10 sitting atop a 2 drawer file cabinet that has been there for several years. I simply put a pi8ece of 1/2 inch plywood cut to size under the tank to distribute the weight. The internal cartridge type filters sold by Tetra, the 10i model, will be adequate for that small tank but will be far from ideal. Any 50W heater, except a Marineland Stealth, which is presently on recall, would be enough for most fish. If you mess up and buy a stealth, just call the recall hot line and they will replace it for you with no troubles.
I always have ignored the advice to separate my bettas from guppies. I have never seen any serious aggression between those species although a betta will sometimes make a half hearted lunge at a guppy, or any other fish.