So. MMR is built off Elo. In Elo we have a K factor, its used to represent uncertainty. Part of adapting Elo into a 5v5 team game with out a dedicated team rooster means we have to adjust to track every player individually.
Part of building a functional MMR/Elo system for team games is to have your K factor change over time.More games played the lower your K factor is. What K factor affects is the amount of MMR your account gains or loses at the end of a match. The more you play, the lower it get until it caps out where you set its lowest point.
If you have rough games, but played a bunch. your K factor will go down. Your accounts MMR is going to be lower for the losses and rough matches. Your going to be distributed into the range of MMR by the match maker at a lower MMR.
And because your K factor is low, your going to need more wins to climb then a new account would.
Eventually you can fix this, like if you play enough the RNG does balance out. Elo and MMR systems do favor good players, its why the bottom of the ladder gets filled with really weak players and/or Trolls. How ever, depending on how the system was built this may take a very high # of games.
Riots claim was 150-300. I have seen some one on youtube make their own Team Elo system and his ran about 400-600.
So you can make new accounts and its easier to climb if you get good teammates. If you climb up a bit and get out of the starting ranges for MMR it will remove the odds of very unskilled new player being put on your team. Trolls will always exist in every MMR but the players who do it every game will drop down to the bottom of the ladder or get banned.
So if your end goal is to just hit say gold. And your not confident in your ability to consistently beat the average player should you have a handicap on your team. Your best bet is to use a high K factor and play when the game has the most instability. (after soft resets, Or when there's a very high # of players with high K factors because the game will make more mismatches where team skills are grossly uneven despite compariable MMR between teams.)
Your attempting to use luck to climb when you do this, and it will only take you so far on a ranked ladder.