You might have to adjust your picks and play-style.
I know that when I was playing in lower ELO last season (this being Silver and low Gold), I found that most people on my teams were picking champions with high DPS/burst damage but little durability, waveclear, or CC.
I ended up playing a lot of Varus, Ziggs and Gragas at those ranks due to the fact that they provided those factors for a team. It helped that both teams kept randomly grouping around objectives and dancing around one another for minutes at a time and those champions were good during sieges and poke-wars.
Also, I've found that players in lower rankings generally don't ward quite as much as those at higher rankings do. I'd recommend switching from Stalker's Blade to Tracker's Knife on Kha'zix (since he seems to be who you are maining) for additional vision. If you can get deep wards in the enemy jungle, you will generally know where they are, letting you:
- Prevent ganks by warning your allies
- Countergank
- Counter jungle
- Hunt them down in their own jungle to kill them
I'd probably recommend building a little more durable than you currently are. Kha'zix should be able to kill an isolated and/or squishy target even without a full AD build, so it can be nice to ensure that you are durable enough to avoid dying. I'd probably recommend trying something like the following since it provides similar damage but makes you much harder to burst down:
[Boots]
