Well, as a Zoe mid main my "kill conversion ratio" used to be very bad for a long time as well as my "vision score per hour".
That's why I only got an "A-" having combat and income at "S-", but "B+" on map awareness.
Eventually I got to fix my vision score per hour by buying more control-wards and remembering placing the yellow ones constantly but smartly (around baron eg.)
Magically my kill conversion ratio went up to "above average" and I think I kinda know why.
In the past I often just backed off after killing someone because of being too low health and mana as well as being afraid of the enemy jungler.
If warded well and aware of the map you can actually predict where the jungler is and therefore either push (and perhaps call your jungler to help you if you can get tower, depending on where he is and if he's behind, even or ahead), going for a short roam or just back off.
The thing is, you need to know whether you are safe or not (depending on where the jungler is and how he is doing).
Sometimes you can even turn a failed enemy gank into a double kill. (Most likely your jungler will be near your side then, so you can ask him for help pushing)
If you back off everytime you kill your enemy laner in laning phase, it is pretty logical that your conversion ratio is kinda bad.
The same goes for roams:
If you succeeded in roaming bot for instance and killed the enemy bot laners while three of you are still alive, don't back just because you are low on health. A fallen bot turret can impact the game so much: Constant pressure botside (you can extend the lead and take drakes,... bc the enemy laners have to deal with bot pressure,...)
Just think of it twice before you back off.
As a tip: Watch pro replays and focus on what they are doing after killing someone during the whole laning phase and try to understand why they were doing it
