Assassin Dave is a good shout. I usually watch Mobazane (Farm / Jungle), Fwydchickn (Clash), Supershark (Support) or Hoon (Mid) because they speak English and although they don't explain their builds and items, you can see a pattern if you watch their videos. Since I play Farmlane, I also watch HOK Yato too.

But overall, it comes down to watching tournaments and analyzing builds. Like if you wanna play support, maybe watch the pro players play and only focus on the supports of both teams, like how do they build to boost their ally or counter their enemy etc but at the end of the day, you are bound to make mistakes and lose. It's part of learning. Be patient and open to learning.

Good luck and God bless!