I agree on the skimmer, but for me that's necessary for any marine setup. I have a 20 gal mantis tank with 20 lbs of live rock and 40 lbs of live sand; a "Stealth" heater (don't get a glass one!); a Remora protein skimmer; a small hang-on refugium; and an Aqua-Clear 20 power filter, with PolyFilter and PhosGuard.
Basically, if you have a healthy 70 gal reef tank, scale the sand, rock, and light down by a factor of 7, put it into a 10 gal tank, add an adequate non-glass heater, skimmer, and power filter, and you'll be good to go.
As far as food, you can always keep the tank stocked with snails/hermits. Small mantis will often take mysis, crill, silversides, shrimp, scallop, squid, fish, etc from a feeding stick or "feeding straw". Feeding 2-3 times per week is usually about right.