You cannot be stuck in gold with a GM mmr because you get 15 points per win and -5 point per loss then. In addition you'd jump 3 ranks or more when ranking up. You'd need a 25% winrate to be stuck.
The way I learned the most about playing ranked (except playing) were the training videos of the professional content creators. KamiVS and Jayflare. There is unfortunately no new content anymore but the old videos are still helpful maybe.