Focus on Learning a Specific Hero or Character. For many beginners, it can be an enormous task to keep learning new characters, especially for those who are new to the game. For example, as Layla gets to the maximum level, she is able to fire at the enemy towers without getting into tower range. That means she is awesome for turret sieges with your team. As long as she is protected, she can fire at will and decimate the enemy towers. It takes a lot of experience to know that, or just internet access and a gadget to access it.
Big Bosses: Turtle and Blue Knight (The Lord). Often times, new players will not pay a lot of attention to these two bosses in the game. The Turtle only gives extra gold for your team while the Blue Knight is a strong boss that will push a lane for you after defeating him. You can have your entire team work with him and try to get towers and eventually the nexus. The best time to do either objective is when you either face the opponent team close to your base or when you catch 1 or 2 players out near the center of the map.
Lane Pushing. This may be an unknown concept to new players. You want your minions to build up so they stack up and they will help siege the enemy tower for you even without you being there. In order to build up minion waves in your favor, you will need to kill the opponent minion waves with your hero so that your minions stay unharmed. Sometime after, your minions will stack up and a huge minion wave will form to help you push a lane.
Never Leave an Ally Behind. I have been in situations like these many times, that if I have a diamond every time this happened I would be rich! Don’t ever leave someone behind, and if you want to leave, warn them first. Also, don’t chicken out in a team clash!
Have Fun. Last but not least, focus on having fun and not be depressed or arrogant on whether you win or lose. In MOBA games, in order to win, you will need to learn to take losses and not be a sore loser about it. Always look to improve your gameplay and learn from each game you play. Focusing on being a better gamer will make you much better off in the long run.