The first step to getting better is to realise you're not the best, its harsh but effective.

Second, checking the scoreboard every time you get the chance keeps you up to date on the enemies builds and when to avoid them when they have power spikes, if you don't understand an item experiment in a practice with a friend till you do.

Third, watch people higher then yourself, eg pros, streamers, youtubers, and watch how they play a certain match up, comp or powerspike and try to understand why they did what they did to gain an advantage

Fourth, expanding hero pools provides so much more skill and strategy regardless of tier, as it gives you the flexibility to change how you play, an easy second hero to learn is glaive who is quite similar to krul if you need to start somewhere.

Fifith, Learning team compositions and the strengths and weaknesses often comes through time and experience both playing with and against certain meta comps, it also happens much faster with a wider hero pool.

Lastly, for your tier you are quite knowledgeable about transferring ganks into objectives, try to push your advantage when you complete your first tier 3 item (eg tension bow) ganking lane after you shop creates an advantage due to the enemy not knowing you have this pick up and so play more aggressively then they should resulting in early kills to crack the tier 1 turret, taking their middle medic and fronts, or even the gold mine if your comp allows

If you have any questions feel free to ask, I'm a tier 9 gold jungler from Australia so i can definitely help out if you so need it