First of all, you have to WIN 75 matches even though it says play, but I'd like to add something else.
I was boosting ranked wins with a friend yesterday, and suddenly I get messaged by the top ranking players who suspected that we were boosting to get the top rank and told us to stop otherwise we would be reported.
I politely told them that we were just trying to get this trophy and then we wouldn't play anymore matches after that.
Good thing they were very understanding about the situation and even invited us to join the community if we were interested (which to be honest I didn't think this game had a large following but it's cool I guess lol).
So my advice is just trade wins back and forth so that you're rank doesn't go too high too fast because it will and they will know! THEY'RE ALWAYS WATCHING YOU!!! lol