Keep going, building on what's already done. But resist the temptation to use too many colors, that easily looks garish.
Consider using different size brushes, different consistency paints, and transparent as well as opaque colors. Don't think and intellectualise the process. Go with your instinct. Let the painting evolve.
And if your instinct isn't telling you anything? Well, just start somewhere, put some paint down anywhere. Then some next to it. Then some over both of these. Try a wider brush. Try a narrower brush. Experiment. See what happens.
If you don't like it, paint over it (or scrape it off) and start again. The lower layers of paint will add texture to the new ones.
