Tankers!
We remind you that the top reward from the free Silver is an XT Skin Container, while the Gold Tier (requires a Battle Pass from the Shop) will reward you with the Mammoth Legacy Skin in its final stage.
By the way, if you think you might have a hard time getting to the end of the Challenge, you can always snatch a Stars Bundle from the Shop and give yourself a nice boost.
Remember, the Challenge ends on Wednesday, January 29th at 02:00 UTC. Hurry up!