I'm pretty new to digital painting also : p. First thing you should probably learn is picking out the right base colors first and learning how to block colors/values in first before going deeper into rendering with a hard brush < 3.
Try starting by doing some photo studies and make sure you do more than only a few base colors. Then after you're done use an opacity gitter (harder you press the more opaque) brush to blend out.
Example if it helps
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