Learning movement around all the maps, specific jumps, shortcuts, vantage points etc. Create custom game modes to practice, this will help you and your team.
Also learn how to move unpredictable when trading fire or moving in general, don't strafe in just one direction it will get you killed and mix that strafing with some jumps it has saved me and gotten me many 1 v 2 kills which helps not only you but your team if applied correctly.
And last but not least... Custom game vs AI or quick matches to warm up before ranked it will always help you out.