Some antiquing will really help once you have the main colors down. You can also dry brush highlights if you’re feeling up to it.
Small detail brushes will help, too. If you don’t have any you can usually get a set of generic ones on Amazon for $20 or so. AND tight area brushes! They’re bent at an angle and are absolutely worth buying if you can find them.
A lot of times in-progress pieces can look messy or iffy, but will turn out better once they’re done.