League just doesn't make sense, I don't even play it anymore. Just a waste of time to me.
For me I went in for my 5 placement games and messed around, really didn't do great at all and lost 4 out of 5 games and ended up in the platinum rank..
So I think for initial placement it has to do something with your kd and spm.
And for jumping up all I can think of is that you need to be ranked high in your division, doesn't have to be number 1 but somewhere up there and just win games.
Played with some buddies that were ranked in like iron or something low. After going on a massive win streak by the end of the night they moved up to gold at #1
And eventually moved to platinum.
I pretty much quit playing with them after that but just the other night I played 2 games with them and they were in the masters.
So I guess if you really want to move up, just play with a good team to rack up the win streaks and it should happen.
To me playing league is just pointless and bound to run into issues, so I just stay away from it