I've been back in this hobby since 1987 and I've always--always--recommended a good single -action airbrush to beginning modelers. (You must first walk before learning to run.) They're very user friendly, easy to clean, and will work well for the projects you'll most likely to tackle as a beginner. You can always graduate up to the more complex and expensive airbrushes once you've gotten not only some confidence but a heavy dose of practical experience under your belt. A Paasche H (set) is an excellent choice for the reasons stated above--it's also a time-tested design. The Badger 200 (I prefer the 200 model with the gravity-feed color cup) is excellent for many of the same reasons. Both would be excellent choices and are sold on eBay all the time at very good prices. Be sure to shop around for the right set--be a hog for a bargain.
(If it were still easily available, I'd also recommend the Binks Wren "B" (medium tip) to you--I still use one and still love it after all these years. It's the best and most comfortable single-action airbrush I've ever used. Binks still supports and makes the Wren but it''s only available from one on-line supplier, and, as a result, it's not cheap any more.)
Well, the simpliest and most practical air source to start off with would be a piston compressor (with pressure regulator) that will deliver 10 -30 PSI. There are many out there, but Badger is all over the place. (Shop around for bargains of course). Important: Be sure to install an in-line "mosture trap" on the air hose, placed a foot or so down from the airbrush connection--and be sure to bleed the condensed water out it often! If you use a paint bottle attachment (as opposed to a color cup model) be sure to get a (tublular) fine-mesh pigment filter that fits over the airbrush's siphon tube. Adding these three things will _greatly_ reduce the annoying problems you'll likely encounter while airbrushing. Then, of course, practice, practice, practice with your "new toy."
Oh, yes, one more thing: Kalmbach Publications, (who sponsor FSM and this website) has an excellent book/magazine on airbrushing technigues and mastering same. Buy it.
The above suggestions will get you past most first-time user difficulties (and remember to always practice, practice, practice with that airbursh set up when your finally able to afford it). Good luck, Jedd.
--Ken