What determines how many League Points I gain from winning a match?
There are numerous factors, but these are the two major ones:
* The difficulty of the match: if matchmaking considered your opponents to be favored, you’ll gain more League Points than normal if you pull off the upset. The opposite is also true.
* The relative MMRs of the other players in your game: if the other competitors are generally higher in the standings than you, you’ll gain more LP (and lose less from a loss), so that you’ll generally trend upwards even with a 50/50 record.
Duo-queuing, and statistics such as your KDA ratio, do not affect your League Point gain. Since your MMR determines the number of League Points you’re awarded from a game, players who intentionally tank their ratings after reaching a new tier will find they progress toward the next division VERY slowly. Essentially, they’ll have to make back the MMR points that they intentionally dumped in order to make meaningful progress toward the next tier or division. There's a lot of complicated logic on the back end to prevent this sort of abuse, so it’s always more effective to play legitimately.