I dont understand the lp gain/loss per game system.

You gain less LP for winning games that the system expects you to win (based on your current MMR and projected MMR, team total MMR vs enemy total MMR) and lose more LP for losing games you were supposed to win. The same is true in reverse, you gain more for winning matches you're expected to lose, and lose less for losing games you're expected to lose.

Going on a big enough winning streak causes the system to think you might belong in a higher division/tier than you are currently in, and will cause it to match you against stronger enemies to verify that. Going on losing streaks causes it to think you belong in a lower division/tier, which will eventually trigger the increased loss/decreased gains scenario while it tests you.

I'm pretty sure these are the things that affect your LP gain:

• Your MMR in relation to your current rank
• Your team's total MMR compared to the other team's total MMR
• Blue or Red side (red team is judged as deserving a slightly higher MMR than blue team)

LP gain decreases as your rank approaches (or goes beyond) your MMR