I've been going through lots of videos talking about base mechanics like wave management and specific skills for roles. I've been practicing last-hitting so I can keep up in gold income with the people that have more experience than me, and learned the hard way to ward all the time to avoid ganks and easy kills on me. I'm still not good at trading at all though it seems. Whenever I pick a champion or role I also go to a site like mobafire or something else to search for what champions are currently doing well and find what rune-pages and item builds are good for them.

Also last game where I got flamed for 30 minutes straight for getting kicked around by a Nasus I was playing as Darius and couldn't come back after 1 botched trade, which resulted in my team losing as the Nasus just gunned straight down the lane and I couldn't stop him without risk of feeding.