If you want to get good, there is only one singular thing you can do to get the ball rolling: map out one book, and then try and finish it. There is no other way to get better but to write and get something out. Finish your first book, not your first series, but a closed group of chapters that ends with the most significant arc. From there, reevaluate. Then do the next one.
You'd want to preferably write every day, zero compromises, even if it's 100 words. Writing is a muscle first and foremost. Secondly, read a lot (something I'm struggling with). The only way you'll become subjectively more aware, literate, and, well, a better writer... It's actually quite straightforward.
Read a lot.
Write a lot!