Your faceit level is Calculated by your elo. I'm on the higher end so I don't really know about lower levels but generally anything over 2000 elo is faceit level 10 (highest rank). Every player (subscriber or not) gets elo but only premium members can view it. The placement matches are based on both your faceit level and how you preform in your games. I've lost 2/3 games before and still got into master so it really depends on your performance.
So to answer your question, you can only rank up at the end or start of a month. Half way through the month you can't go from gold to master for instance. You can however rank from faceit level 9 to 10.