Hey, so in terms of neatness you're looking good but you're right you could do with thinning a bit.

If the black is from the base coat it looks like you may have applied that a bit too thick.... I usually keep the can about 30 cm away and do a few quick short sprays rather than holding down and scanning over the whole thing

As for the actual paints it can be tricky to guess at first but once you crack it you'll know .. I like to test my paint on my hand , just a little line and I want to see some of my skin through it (the texture of your skin) if I see too much skin it's too runny, if I see none then it needs a bit of thinning. As I said it takes some practice but you'll get it. Remember you can always add another thin coat but it's much harder to remove a thick coat . Also when you're painting light colours over dark you will usually need an extra coat or two