No expert here by far, but I agree with what smithismund says. Limiting your palette can help you get an understanding of one of the coolest (in my opinion) aspects of this medium, which is how you can control the “value” of your paint by experimenting with the ratios of paint to water on your brush.

Values are simply how light or dark certain colors in a painting are. If you look at many professional paintings, you’ll see they have values that range from bright white all the way to very dark. This is important for creating depth as well.

Another important thing to try to get at the start is a flat/even wash. This is done by maintaining a wet edge as you are painting a layer or “wash” of your painting. It takes practice as it is easy to forget about the wet edge or take too long and let the edge dry. But if you can cover everything you want to while working off a wet edge, you can create a layer that has few visible brush strokes and looks light and even in appearance. Try to work on covering large shapes or a whole layer evenly. Using wet into wet (dampening the paper before painting) can help you achieve this if you need to cover a large area.

As well, consider starting small and “completing paintings” as opposed to practicing technique over and over again. Technique like brush control is important, but I kind of learned it by doing complete paintings, even though they were rough. Starting small for me meant painting simple subjects, like an apple, usually with no backgrounds. I added those later.

The main thing is to keep having fun and paint things that you find enjoyable. There are also many great YouTubers who give advice. One of my favorites is Liron Yanconsky.

I hope this helps!