Supplies Paint for Airbrush

Gimme a moment to gather my links, I wrote this up in the past for a couple people already

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First, the Mr. Hobby Aqueous colors. I use them for painting details, but you can also airbrush them.
They need thinning before you can airbrush them, and getting the paint out of the glass can be a bit of a pain. Have very funky metallic colors, but be aware that the pigments clog the airbrush quickly (more about that later).

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Vallejo Model/Game Air, reaaaally comfortable to use. Smell nicely, dry quickly, need minimum to no thinner (depends on the needle size you use, and if it's a metallic or not paint).
Built in dropper makes it super easy to get out the paint/get out the right amount.
Have a lot of normal colors, regular metallics and also some effect paints (like color changing ones!).

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Schmincke Aero, come in big glass bottles with a dropper tool included in the cap. Minimum to no thinner needed, depending on the paint. I personally never used them that much, but they got some really nice effect paints.

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I only have one Ink, and it's metallic so it's a bitch to use anyway

There are also lacquer paints, like the Mr. Color ones from Mr. Hobby, or paints from Tamiya's Lacquer Paint line. They need a different thinner, and are pretty popular among model kit people.
The reason for that is that a) they are more durable than acrylics and b) they airbrush nicer (dry faster, thin better etc.).
However, they smell horrible and you really need good ventilation with them. Acrylic is the safer option.

I started using lacquer when I made my Nendoroid customs, since those are supposed to not be customized again and be pretty durable. I am not sure how good they are on resin that might be repainted later on (i.e. whether it will stain sealed pieces or not).
You also need to be careful with mixing lacquer and acrylic. You can spray acrylic on top of lacquer, but not vice versa. Lacquer is too "hot" and will damage acrylic.

Lacquer I thin with Mr. Color Thinner (which is at the same time the remover as well).
Acrylic I thin with Tamiya X-20A thinner.

When you thin paint, you want it to be like...well, they usually as example use skim milk (so the low fat type). Not water like, but also not...thick. You get a feeling for that. When it's thinned too much your paint will be runny, when it's too thick you will struggle getting a fine mist/it will clog the airbrush.
Also, if your air pressure is too low it usually dries rougher/more coarse as well.
Basically you want to have it thinned just right, with the right pressure, that when you apply it it's a fine, moist layer. Not running wet, not drying immediately. Otherwise the finish will be pretty coarse.
If you feel it's too moist, you can gently blast some air on it to help it dry faster before the next layer.

Now back to the paints: the ones that are already made for airbrushing, tend to deliver a finer result.
That makes them especially useful for when you want to "fade" from painted to unpainted areas. Like a pair of hooves where you airbrush the hair and then it fades into the skin, or especially on the face!
I really like the Vallejo Air colors for that, because they are already pretty thin by default. With the Aqueous ones I sometimes struggle properly thinning them to a point you get the same fine fade.

Metallic paints are gorgeous to airbrush, because...honestly, it's the only way to really get that effect vs. pastels and dashing on metallic pigment.But they are a bitch to use. The metallic pigments are quite big vs the regular paints, and when you thin them they sometimes like to do funky stuff (separating the pigments from the rest of the paint). They work better with bigger needle sizes (I usually use 0,4mm).

In short: try to get acrylic paints that are already made for airbrush use, those are the easiest to handle for a beginner.
I would highly suggest Vallejo Air bottles for that