MMR gain?

[lolyou]

Do you get a random amount of mmr points after winning or does your performance affect how much you get?

[quicki rabit]

Your points gained in match do not affect on how many mmr you get. Most of the time you get 9 mmr for win and 9 mmr for lose but it depends on how many mmr other people in the lobby have.

Additionally when there is a new season the first 10 matches are placements for which you get more mmr, there is also a bonus for several matches after completing placement matches.

[(TTV)OnBrandRP]

Originally posted by LOLYOU:

Do you get a random amount of mmr points after winning or does your performance affect how much you get?

MMR is tailored by stats in ranked and has a soft cap. The soft cap is basically your average MMR. Once you reach the soft cap you can never go below the soft cap.

Which keeps you in a level playing field. It's basics of competitive systems.