What are the Best Roles and Builds for each MMR/ELO Level to Climb With?

Last year, I saw a bunch of good players taking the challenge to climb with a certain role in X amount of games to the MMR cap. The game and player base changed a lot since then and wanted to try the challenge to compare/contrast. I haven't been in the lower MMR/ELO in a while and wanted to know the more favorable roles/heroes and their builds.