How to measure improvement for new players?

Pretty self explanatory, I’m new to the game, love it. I’m not too great at the game but I’m trying to learn all 3 roles so I can be flexible depending on what the team needs.

My question is for each role, what should I be using to measure my improvement. Ik winning would seem like an obvious win but you could also just be getting carried by good teammates. At the same time I would imagine it’s a lot more complicated than just looking at raw damage/blocking/healing stats