Valid for any class/spec you want to pick up:
Look up the build r1s are picking for the bracket you’re queuing for. Queue a few games and take note of how early you die and how much damage/healing you do. Take note of what skills you notice you aren’t using.
After you get a few games in, tune in to their stream’s vods and see how they play with the same build. Notice the difference. Notice what buttons they’re pressing to do damage, like, actually look at their skill bar or the addon they usually have that shows their last used skills.
This will give you the highest skill returns for the lowest time invested. Do it over a few days and your skill should go up by a lot. You’ll start noticing things that you didn’t before.
Also ensure you’re using the correct the itemization by, again, copying their stats.