Before reading, please understand that everyone has it's own opinion - if you do not agree, stay calm and polite, respect others.
Since, I'm new to forum, however playing MOBA games for over than 10 years, then I guess that's one of the best spots for me to introduce myself as well as give you some tips regarding our beloved "Ranked" matchmaking.
To make sure I'm ex Semi-Pro/Pro series Dota 2 player. Attended to be in a top 1 team in my country.
1. The most common and general issue. Whenever you play solo in ranked matchmaking, focus on yourself, not on your teammates. You're not playing with your friends, there will be less team play for like 80% than it could be. That's why I'd suggest firstly prevent - spamming, raging, flaming, feeding, count the impact of your teammates in the game. Since you're playing "Solo" ranked, do the best you can do from your side without watching at your teammates, do your best as individual with outplays, split pushes , big moves. Don't fight against enemy as you'd fight 5v5, remember that you are playing "Solo" ranked, that's why you should expect less help from your team, find pick offs in this case and after - take advantage out of it.
2. Don't spam 1 hero as most of the people love to. I've seen there some people says "If you want to master *hero*, you have to be played 250-500 games, depends on the hero. How you can master a hero, when you mostly will do same thing as usual? That way, after 20-30 games you will be mastered that hero for sure. Of course, for some it might take and 50 games. If you truly want to master your beloved *hero*, pick different heroes even all heroes, learn them, know what they can do and where is the limits of these heroes, then you will know how to act with your favorite one against any specific hero. I do highly recommend to have at least 5 signature heroes for your desired role, that matters a lot. Even if you play "Solo" or not, you will have more choices to make and more combinations with other teammates heroes.
3. For god sake, don't simply pick gear from "popular equipment sets", "top player sets". They have their own play styles, it means you might play totally differently. Read all items and make your own gear even if it will be the same. You will act totally differently in-game after that.
4. Don't ever chase, seek or anything like that for a kill. Play smart not greedy. That is the main key in MOBA games. Your main and only targets are towers and the main building. Don't fight if you're not going commit for a tower. Don't search for kills if there is no creep wave or anything like that near the tower. Focus on farming and objectives, not on the kills. If you are fighting for nothing, you're wasting your time as well as giving more time to your opponents to grow. Kill means nothing, but kill and objective or even only objective is the key to YOUR victory.
5. Stop being rude regarding statistics, since it doesn't mean anything. There can be even TOP players with no "Maniac", "Savage", Lots of "Triple and Double" kills. Since after all, you're winning not because of that you've killed enemy player, but because you're eliminating their "Throne".
These are my 5 main rules to myself playing MOBA games. That's why currently I have 77.78% Win Rate regarding "Ranked" matchmaking and playing "Solo".