Play all the roles and learn how they work (for example: if you play support alot you start to learn how to act as an adc to work with your support, I can say that there's nothing more annoying than sacrificing myself as a support so the adc can survive, only to have the adc turn around and suicide)
Play characters you have trouble against, after you get creamed as wukong from somone who buys oracles, he's no longer as intimidating, or as hard to beat.
Learn to predict which direction people will be when i skillshot lands, this makes the difference between hitting 50% of your skillshots, and hittting 80%.
Likewise, learn to predict and dodge skillshots, this allows you to make somone such as morgana waste her most important skill.
Last of all, work towards rediculously good map awareness, this is definitely the hardest but try to call mias for teamates that didn't notice them. Don't be the one who walks into a group of three roaming the jungle. This is one of the less important ones if you already have good map awareness and also one of the hardest, but this goes a long way towards compensating during those games when you have idiot teamates.
I can't guarentee that these will help, but these things are severly undervalued and at least give you things to try to improve. I hope this helps!!!