Okay, let's look at what's needed for gas and nitro separately.
Nitro first:
Engine
Fuel(normally 5-15% nitro and 16-20% lubricant, depending on engine requirements)
Glow Plugs
Fuel tank
Nitro compatible fuel line
Glow driver or battery and fitting(a nitro motor is similar to a diesel in this regard, there isn't an ignition system since, once the glow plug is hot, it will stay hot as long as the engine is running)
Fuel pump
Prop
Engine stand
Starter and battery or "chicken stick"

Now let's look at gas engines:
Engine
Prop
Ignition system, if not part of the engine from the facory
Fuel tank
Gas with lubricant mixed in per engine requirements(usually between 16 and 32:1 IIRC)
Gas compatible fuel line
Fuel pump
Engine stand
Starter and battery, "chicken stick" or protective glove

Just to be clear on a couple of things:
The fuel pumps are just to fill the tank, not to feed the carb.
A nitro engine will need "exhaust pressure" to get a constant fuel flow. There is normally a pressure tap on the factory supplied exhaust just for this purpose.
A gas engine, depending on the carb, may have a fuel pump as part of the carb so exhaust pressure may not be needed. This will be normally talked about in the owners manual
Not all gas engines need an ignition battery. I have a CMB 27cc marine engine and it doesn't require one.
A battery pack would be needed for your radio gear, regardless if one is needed for the ignition. IIRC, you really don't want to run the radio and ignition off the same pack as it will drain the pack much quicker than either one will by itself. You will also notice that I added a prop to both lists. You don't want to run an engine without one as:
1) it won't get proper cooling and that will cause damage to your engine
2) the prop works like a flywheel on a car engine, giving the crankshaft more mass to help keep the engine running. It may not run without one or, if it does, it won't run well

I'm sure others will have more to say about this as I don't claim to be an expert