I dont mean this personally...but step one is to change your attitude. Not trying to be toxic...if you go into every game feeling like you're not able to contribute shit, that's just a self-fulfilling prophecy. If its any consolation, so do I. It's the same reason why I wait forever before playing my placements - I personally feel like this entire playerbase loses like half their fucking IQ at the season start, and after like a month or two, they MIGHT have enough of it back that I can play a game without a 0/8 inting ADC shrieking to report me in all chat for not constantly standing on top of the enemy laners instead of walking behind my minions when im on CD. I do not deal with the initial start of season well, because imo, NOBODY does. Start of season, and like last 2 weeks of season, are imo the most toxic fucking games ever, and I do not play nice with people who dont play nice. I dont need another account ban.
Step two...sort of depends on what roles you play, and honestly, what your rank typically is. From what I can gather, you play jng/support, right? Sorry for snooping on your op.gg >.>
I'm not sure where you typically fall in ranks, so I'll use myself as an example. I run either role in bot lane, mainly...I don't personally like BunnyFuFu's streams...but I don't deny his skill at the actual game. Sneaky and Aphromoo are still fun to watch. I say all this because as much as I hate watching worlds itself (competitive play is much, much different from solo queue) I do feel like watching these people play in solo queue enough helps you to sort of get a glimpse of what you consistently screw up on.
The rest is just practice, and praying to the Riot Overlords they don't match you with iron 4 in a gold game, or match you with Nubrac's "support" Teemo. >.>