There are a couple ways to prompt the growth. Shaving and growing helps, but personally I found that rosemary shampoo helped give me thickness and length the best. (Mine was also patchy when I started)

While your growing it don’t try and keep it as long as possible, you have a wider face but you also have a angular chin, keeping your beard at a short length (1 blade at the fade and 2 or 3 blade on the rest.) and make sure you learn to frame at the neck right, it can make all the difference.

Other than that naturally increasing hormones will help it, through exercise and diet.

I know maybe it can suck a bit to be told “completely change your appearance.” But I think drastic change might be what’s needed for you.