For the air compressor, the 2 most important things are a steady adjustable flow of air and no containments. Some people might argue that the compressor makes is important, but I do not think that the discomfort from the sound of the compressor makes should distract you from the quality of your compressor.
A number of cheaper compressors are on the market without a regulator, regardless I would suggest that you have 2 regulators, one on the compressor, and a second one that can clear out any containments. Most of the compressors do not have a regulator with a filter built on/attached to the compressor so this would be the second item you will need to purchase.I purchased mine from Craftsman with a part # of 16022.
Of second importance is the quanity of airthe smaller the tank you purchase, the more often the compressor will run and the more often your airflow will be slithly lowered. For most models, 1/35 and smaller scales, a large tank size is not important as it would be for the larger scale items. Something 4 gallons and larger would be overkill but acceptable. A smaller size one will work fine for small scale models. the choice is yours. Also to consider, is the PSI (ounds per square inch) that the compressor can deliver. I would suggest a compressor that can deliver at least 50 psi, as sometime the extra air may be needed to clear a clogged airbrush.
Might I suggest that you consider a Craftsman brand aircompressor. Pound for pound and size for size, they be larger than what your LHS can give you, cheaper in the short and long run and you can generally find a Sear/Kmart right around the corner for parts/service. A great incentive instead of spending a hunder + dollars for a product that is only available VIA mail order.
BTW: I didn't mentioned it, but depending on what paint you are using and your rate of thinner to paint you will normally be painting in the 5-15psi range.