I need help improving...

Hey so I'm really not sure what else I can do. I don't want to spend money for coaching so I'm hoping someone can help me figure out what to do.

I really want to climb in flex to gold. I'm gold 5 in solo but more worried about gold in both. I do everything I can to try and fix my mistakes, rewatch my games, take notes where I mess up and avoid making those mistakes. I'm constantly getting wins and losses and never get anywhere. I randomly dropped from silver I to silver II 0 lp and it's getting worse. (I do have my bad games where I play until I'm titled and I guess I shouldn't play at that point but still do)

Also..:Now I'm not blaming my teammates but how come I'm getting a team full of 1 gold player then bronze and silvers while the other team will have 2 plat players and higher mmr than my team?

I don't think I deserve gold but maybe someone can help me figure out what I'm doing wrong in my games so I can reach that level of deserving gold and gaining that Elo.

I main mid and support. Diana is my one trick and I do well with her but maybe she's just not a champion I can carry with? I'm not sure...