Completely new to airbrushing, advice on next steps to take

I think you can get into airbrushing for your $100. Here's a couple on Ebay:

www.ebay.com/.../190749076540

or better, this:

www.ebay.com/.../191210499970

or go to Harbor Freight with a 20% coupon and buy their compressor and deluxe airbrush total ~$100

None are top-o-the line but do work and should last quite a while. I have and used the HF ones for over 3 years without problems but have since gone to other AB's and a tank compressor. I think the ones listed above probably come from the same factory as the HF ones. Just some thoughts.

I picked up a very quiet no-name airbrush compressor with tank, from eBay for $89 with free shipping. It's WAY, WAY, WAY quieter than my Porter Cable general purpose compressor that I had been using, which basically sounds like a lawn mower. I've had it for about 6 months, use it every weekend, and have experienced zero problems with it. You can also find some decent Chinese made airbrushes in the $20 to $30 range. They're not exactly Iwatas, but they'll serve until you can afford an upgrade.

Most general purpose compressors are loud (but less expensive).  Some compressors made for airbrushing are quite quiet, but more expensive.  You get what you pay for.

An intermediate cost solution is to buy a cheap but noisy compressor, and a portable air tank.  Fill the tank in the garage with the compressor, take filled tank down to workshop. I know a couple of folks who use this solution.  This requires a small regulator on tank, but regulators are not too expensive.

You might look into CO2 for an "air" source; no moisture in the line ever and no noise at all.  I like my set-up.  Just a thought that might work for you.

Gary