So, just going by your match history, a couple things jump out. Keep in mind that I am no where near a high rank, this is just from my experience.
#Map Awareness
Simply put, you hardly use wards. Yes, I see you using a few here or there, but honestly you aren't using nearly enough. And if you are using little to no wards, I can tell you aren't looking at your minimap. This is a skill you need to learn. For example, take this match:
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1505003530/33063766
In 42 minutes, you used 2 wards, both from your trinket. Assuming those were placed post lvl 9, 4 minutes of coverage. If they were used before lvl9, that is 2 minutes of coverage. This means that for 38-40 minutes, you were not helping your team with vision. Remember, vision is everyone's job, as since the vision changes 1 champion can no longer cover the map. Compare that with my most recent game.
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1510370699/33573269
In 52 minutes, I placed 24 wards. 7 of those were normal wards, 2 were vision wards, and the rest were from my trinket. 21 minutes I had coverage for my team from my purchased wards alone. Assuming all my trinket usage was before level nine, this means that my trinket gave me 15 minutes of coverage. Post lvl 9 trinkets would double this, meaning it would have given me 30 minutes of coverage. This means that anywhere between 1-16 minutes, I was not helping with vision coverage, not counting my pinks. Obviously these numbers are off, as I used multiple wards at the same time, but it is a good way to demonstrate my point.
You might have noticed I discounted pinks. Pinks are immortal as long as they are not destroyed, so it is completely worth to pick one up early and hide it in a spot that will show you incoming ganks. I did this last game, and you would not beleive how many times someone walked through the bush I hid it in, and didn't even notice. Seriously, they had no idea, and kept walking through it. This is with people in mid-high Silver and low Gold.
However, placing wards is only half the battle. Keep an eye on the minimap. See someone in the jungle lit up by a ward? PING THEM! If it is an incoming gank, use a DANGER ping. If it is someone easily picked off and out of position, use a normal ping. The pings alone allow you to share your map awareness with your team, increasing your odds of winning.
#Objectives
This one might seem obvious, but it needs to be said. You need to focus on your objectives more. This means Towers, inhibs, the nexus, Dragon, and Baron.
Using the above games, while your team did take a couple dragons, they did not really go for towers, and while you did get baron it was too little too late. Remember, the point of the game is to knock down enough towers to break an inhib so that you can ultimately take down their nexus. it's OK to lose a dragon or even baron if you can take a tower or two without dying or losing your own tower. Dragons respawn, Towers don't, and inhibs put a lane into auto push mode, forcing the enemy team to push it or ignore it at their own peril. If you gank, or push the enemy laner out of lane/kill them, PUSH THE TOWER! Keep an eye on your minimap so that you can be aware of ganks, but do as much damage to the towers as you can. This will at least whittle it down, allowing for another push to just breeze past it a little easier.
Looking at my game, you can see that it was pretty close. They got an early lead on us, getting several towers and a dragon. But we also had a dragon, and kept focusing the objectives, and it paid off, allow us to catch up and eventually blow past them in gold. We got a baron by trading an Inhib, and were able to crush the enemy team from behind. We then IMMEDIATLY pushed, giving us our first Inhib and putting us back in the game.
#In Summary
Work on using wards to the fullest, and paying attention to objectives. This should help you start getting better.
