Can a high Elo player give me some tips to climb?

I’ve been silver for 2 seasons as a one trick Diana main and I’m ready to get better by improving my game knowledge.

I would really appreciate it if a higher elo player explained to me eeeeeverything I need to know about the game which I may not be aware of (Wave management, what to do with leads, roams, wards, contesting objectives, when and when not to split push, etc).

One thing that frustrates me as a Diana main is when the enemy have a fed Garen / Nasus / any fed bruiser. They’ll destroy my team even if I jump on the arc, since someone like Illaoi can easily 1v4. And more often than not, if I’m A fed Diana jumping on their adc, their top lamer would focus me in team fights and I’d be useless.

I’d love for some tips, I hope it’s not too much to ask.