So you are speaking for someone else’s experience, right ?
I personally leveled up quite fast to rank 15: I think something about 40 matches with a good ratio of winnings.
It depends a lot on your victories, not your played games: there is an algorithm to calculate this, and I couldn’t find a specific explanation, but I noticed that it takes about 3-6 winnings to level up ( in the first 20 ranks ) and 2-3 losses to go down. Of course at level 30 it may be 10-12 winnings to go up, but on lower levels is quite easy.
The hardest thing is that you have to play with some good teammates, because most of people play in team.