First of all, the most important is your mindset. You will never progress by blaming your teammates, being toxic, not using your mic, getting super tilted super quickly etc. You always have to be positive, it's ok, anything is winnable. No backseat gaming, no focusing on your team's mistakes. Just play together.

Secondly, stats don't equate to skill. Just because you can go 15-5 doesn't mean you're a good player. Getting better means playing your character properly, and making the right decisions. Also, try not to look at the scoreboard. You may tilt if you are not doing well.

Another thing that held me back at first was not warming up. Not warming up because I was just too excited to play, I wanted to get right into the game; and I'm still like this. But, I have the discipline to warm up, spend 15-30 minutes practicing my tracking, crosshair placement, flicks, trigger discipline and decision-making. I got a lot better when I started doing that.

Watch pros. Watch pro matches in particular, see what the commentators say and evaluate certain plays particular to your agent. Trust me, you'll learn a lot without even realizing it. You'll be able to pick out others mistakes a lot more. BUT don't constantly tell them their mistakes.

After I learned all this, I was still hardstuck gold, but I knew I was better than golds and even some plats, because I didn't make all the same mistakes they did, and I was frustrated; I wanted to quit sometimes. But I ran into this guy and holy shit was his aim bad, but he was definitely smarter than everyone in the rank. We were hardstuck gold together, but since we became friends and we both could accept criticism, we helped eachother out.

Fast forward one week, I meet some of his friends he meets some of mine and we have about 12 of us in a discord server, then we started 5 stacking.

If you're hardstuck, it's very possible it is your teammates but you should always focus on your own mistakes rather than theirs. Right after we began to 5 stack, we went on an 11 game win streak with the new season, because we were all better than gold players but we were stuck there because of our attitudes. We had great chemistry, and I really hate to say it, because I know not many people have much friends, but you have to stack.

If you're better than the rank you're in, you have to stack. Not with just anyone though, it has to be with people that are just as capable/reliable as you. You can't be stacking with people who are negative, toxic just because they're good because you'll lose games. Trust me. Stack with people who have good mindsets, because once you start becoming friends you can help eachother out with plays, and warm up routines etc and you can grow together. Our friend that was gold 3 with us, got to immortal in a matter of a week when we started playing together. We knew he was good, but we didn't know he was that good.

Now, let me make this clear. This does NOT mean you can just blame the fact that you're hardstuck on your randoms / not having enough friends. ALWAYS look into yourself first.

Obviously this isn't everything that got me to diamond, the rest is the basic stuff that everyone else will tell you. Just know that it takes time to improve, it's not going to happen over night unless you're a very very fast learner. Give it patience, and good attitude and you have to trust in yourself, and your team. Players in platinum and below, are not that good. Even some diamond players aren't, a lot are boosted; or have all aim no brain. Don't be that player, it's better to have better game sense/knowledge than to have great aim. My aim isn't that good, I can barely get 20 points on the medium bots in the range. You just have to be smarter.

If you have any questions I'll be happy to answer them, I hated seeing all the other Reddit posts from other diamonds who talk about the same shit and give advice that spoiled a lot of my experience in-game. Not all advice works for everyone, but don't spoil people's games.

Edit: people are literally only taking it that you NEED a stack to rank up. In the first paragraph I said not to blame your teammates. If you're a bronze player, you won't get to diamond by stacking. You HAVE to look into your own mistakes first, you have to solo queue to gain the skill to prove you deserve a higher rank before you stack. Stacking will rank you up but you won't gain as much skill while ranking up. Stacking is not the secret to ranking up, learning from your mistakes is.