Get this through your head since it's general.
1. No flame, 0 flame, zip nadda, not a bad thing comes out of your mouth towards another player. If they're being toxic just mute, not worth your time. Remember, you alone are responsible for you getting better- not some fucking douchenozzle online. Don't blame them, move on.
2. Play simple champs, it'll make you understand the basics better.
3. Kind of ties into point 2, but lessen your champ pool. It's not healthy to play a lot of champs, recommend three for each role you specialize in.
4. Always practice, no matter what. Seriously, take the time to write notes in-game too after you win or lose to note what you did right or wrong.
5. Do not treat wins or losses with any real value, improving at the game is more important than some imaginary fucking number.
6. If you're tilted, don't play, period. If you need help unstinting there are plenty of guides but my advice is to play something else. Maybe less stressful.
Do all of this and you're basically on the right path.