u want to start out with a good air brush and stick with it. i have the badger krome( amazing air brush) for compressor i would get a iwata power jet plus since it saves space and it come with an build in air tank.
No, that’s plenty big. I use a .2mm needle with enamels and have so far not encountered a single clogging problem. Just make sure that the paints are properly thinned.
The Krome comes with a .2mm and a .3mm so that will serve you very well. You can use the .3mm for metallics as they are usually a little thicker .
A good way to start is using pla-plates! They are thin plastic plates that you can cut up and glue on kits.
Also scoring panel is another great to add details, but the placement on it is important. By adding pla-plates and panel lines u can bring out areas on the armors to look like a MG kit, bit remember not to add or else it can look mess.