Welcome to the wonderful world of firing paint at stuff whilst trying to look all professional.....lol
Acrylic or Enamel... well that's down to a personal choice, you'll end up using the type that suits you best... personally I never got on with enamels, and prefer to use acrylics... however some guys on here can get fantastic results with enamels ..
There's a million and one different ideas for what to thin
paints for airbrushing with, personally I tend to use the propriety thinner from the paint you are using ..etc Tamiya thinners for Tamiya paint.. and so on...(although Tamiya do produce a lacquer thinner for their paint and it's brilliant.. really works well with their Acrylics..) also be wary that one company's thinner may not work with another company's paint,
for cleaning the airbrush afterwards I use 99 % Isopropanol Alcohol ... (it's cheaper than using a propriety thinner to clean with)..
As for thinning paint, I use the rule of thinning it to the consistency of milk. sometimes I'll add a drop or two of 'flow improver' just keep the flow consistent, and cut down on 'tip dry'..(where the paint starts to dry on the tip of the needle, and then causes inconsistent airflow)
As for set up, my advice would be to purchase a compressor with a tank fitted to it, the tank will store a constant and stable supply of air whilst you are working with it, and stop any 'pulsing' from the compressor..
have a look around Youtube, there are loads and loads of video's that introduce you to using and airbrush, these are quite informative and easy to understand..
for example...
hope this helps