What budget do you have for airbrush and paint ?
Iwata airbrushes rock, I've been using them for over 25 years now and I can't fault them, worth every single penny !
I recently bought one of these
https://airbrushes.com/product_info....6083c4bff62535 from the airbrush centre, stunning bit of kit if you just want to lay down colours and do fades, maybe something finer for smaller details but essentially this would do you to start and isn't too much cash.
The above mentioned has a bigger nozzle so not too much thinning required however it is advisable to thin the paints slightly, maybe 10 - 20% just to help it flow a little better.
What air source do you have ? Do you have access to a compressor or will you need to buy one of those as well ? I use Bambi compressors, brilliant bits of kit and no louder than a fridge so won't irritate the neighbours. They aren't cheap but this place knock them out for a very very low rate -
http://www.aircomps.co.uk/product-ca.../bambi-budget/
Hope that helps to get you started.