If you want to paint large areas of people, you might want to consider a small spray gun instead of an airbrush. I don't have one yet, so I can't give too much advise on that.
If intent on an airbrush, you need to decide if you want a single action or double action brush. Once you learn to use it, a double action gives you more artistic techniques, but a single action is cheaper and easier to clean.
I don't recommend trying to save money on the brush itself. A cheap brush will give you all kinds of headaches that you don't need to be dealing with as a beginner.
For doing makeup/body paint, I pretty much only recommend the Iwata Eclipse if getting a double-action brush, and the Paasche model H if getting a single-action brush. Both are designed with a larger diameter nozzle, that allows thicker paints to pass through more easily, and is less likely to become clogged.
Portable air is a bit tough. Many machines are either very very loud, very very large, or provide low uneven pressure. It can often be difficult to get specs on the noise output of the compressor. I'm told that there are some newer Japanese models that are very nice, and smaller than a loaf of bread, but I can't recall the names.
One solution that I use for portable air is compressed CO2 tanks. Don't confuse this with the bottles of airbrush propellant you might see in the craft store. Those are pretty much garbage. These are the sort of CO2 tanks that are used in paintball guns. To use one, you need to use a special regulator. Lowes sells them under their Kobalt brand. Something like $130, but I think it also comes with like, a nailgun or something. You'll likely need a few adapters to get their connector to fit your air-hose. Some must use teflon tape to seal it, others must not use tape. Leaks in any airbrush system are really annoying. The downside of CO2 tanks is that you need to know how many tanks you need. Once you run out of air, you need to either find a Lowes, or a paintball store to sell you a recharge, or you're done.
At home, I just use a plain pancake style air compressor from the hardware store. It hooks up to an air filter and a second pressure regulator. I keep the compressor in another room to abate the noise, and because the long hose helps to bring the air closer to room temperature.
As for makeup, I never buy the premixed stuff. I mix my own using either moist cake makeup like Kryolan's Aquacolor and water, Alcohol Activated makeup like Skin Illustrator and 99% alcohol, or occasionally, PAX (Prosaide prothetic adhesive plus Liquitex acrylic paint) mixed with a bit of water. Ya gotta be careful when airbrushing PAX. If it is left to dry in the airbrush, you are in for hours of careful cleaning to save the thing.