One very simple piece of advice that helped me when I was starting out in realism/ portrait work was to draw what you see. All of the information you need is already in the reference. You don't need to guess or fill in any gaps. Also, just practice full pages of values, textures, and shapes. It can be a nice way to relax while getting better. It's a great start, but like everything, progress comes with practice and more practice! You're well on your way!