PSA: No matter what, don't dodge games during you placements
That will absolutely tank your MMR because the system will take the dodge as hidden loss. So if for example you dodge 10 games then win all your your placements, your actual standing won't be that you won 10/10 games (100% winrate), but rather that you won 10/20 games (50% winrate).
The reason I'm writing this is because even though it's well after RIOT confirmed this, people still believe in the urban legend that you are free to dodge placement games because there's no LP system. Just today I had somebody dodge because they were in their placements and the enemy had a Lulu/Kogmaw botlane. DON'T DO THAT. It's the definitely the worse thing you could do to your MMR. Never, ever, dodge your placement games. It's better to take your chances with a probable loss than getting a bonus loss for absolutely free.