As far as auto body goes, use a quality acrylic paint (not 2 pack), and go base and clear. Metallic isn’t really any more difficult than a solid colour, provided you use the right technique.
The only issue you’ll encounter with metallic that you won’t have over a solid base, is that the metallic flake can fall over (or is pushed over) as you spray. You need to spray a mist/dust coat prior to clearing to give a uniform appearance. If you don’t do this, you’ll get tiger stripes through the paint under the clear.
There are a few advantages to base & clear as a DIY’er.
1) if you ever need to blend for a repair, whether it be metallic or solid colour, it’s a much easier process with better results
2) Additional UV stability and deeper gloss after wet sanding/polishing
3) Minor damage to the clear coat won’t impact the colour underneath. For example, an oil spill on some acrylic paints will permanently discolour it. The clear coat can be wet sanded and polished again.
For a vehicle that you just need to get back on the road quickly and don’t care for colour matching and ease of repair, go a single stage acrylic (solid base only).
If you want a really nice looking paint job that’s very forgiving for a beginner, go base & clear. Runs are very difficult to sand out properly, so with an acrylic base/clear system, you can spray a little drier without compromising the quality of your spray job. This means that you’ll need to deal with a little more orange peel when you’re wet sanding.
Being a beginner, you’ll be wet sanding regardless of the paint you choose.
Two pack paints are another realm again, but I wouldn’t suggest you learn with them as 2k is not as user friendly, especially for a home job (aside from the health risks).
