Back when I was a student and even after I was out of art school the thing that helped me a great deal was copying a Masters painting. Many may think it is cheating or even not right to copy a Master Artists work... but that would be wrong. Copying a Masters's work was done by the Masters themselves when they were students themselves. When reproducing the work of a great Master Painter you learn a great deal about so many things. The Master painter has figured
out quite a bit that will come much easier for you because of the fact the master has already done the difficult stuff for you since the Master has spent a long time learning their craft.
Copying a Masters's painting is like a class in itself. you learn about the composition the master chose. the drawing, the application of paint, the value pattern, the colors, and how the master handles their particular subject matter.
I had copied a lot of Andrew Wyeth's work and John Pike's work because I loved their style and subject matter. I can't even count how many I had done. Sometimes I would even copy an oil painting master's work and then do it in watercolor.
I suggest you find an artist Master that you like and that master doesn't even need to be a Master from the past, it could be an artist that is alive today and you just love their work.
The only problem with copying a master is if after you copy it you say it is your own and you don't give the master credit. Just a simple giving the master the credit for the painting you copied is enough to show viewers it is a copy of a Master. A good way to sign the work you copy of a Master is to put "AFTER JOHN PIKE By David R Becker" if you copied a John Pike painting.