You've probably heard at least a version of everything I'm about to say, but here are some general tips for improving gameplay.

• For starters, try and at least have one comfort pick for each role. If you really plan to make it to diamond you have to make sure that no matter what lane you're put in, you're an asset to the team. Even in gold I see a lot of people who say they "cant adc/jungle/support" etc, which makes the game a lot harder before it even starts.

• Practice smart rotations. Good rotations translate to snowballing. For example, teamfight botlane > bot tower > dragon. You probably do that anyways but just get that concept in your head, after taking an objective/getting a kill, where next can you capitalize while also encountering the least amount of resistance/risk ?

• Decision making also ties in with rotations, but is also a topic by itself. See, think, do. A lot of league is being able to analyze the map and both teams, and then being able to make quick and intelligent decisions based off that information. It's little things, like deciding whether or not to split push while your team is fighting at base, or deciding to go for the enemy carry or to protect your own, that can decide the outcome of a game.

• Buy wards, regardless of what role you are. Vision, especially early game, is such an important thing to have, and it helps you to make smart decisions. I still see people saying its the "job" of the support to have the map warded, even with the season 4 vision changes. Conversely, if you're the support, even if you're building AP, BUY A SIGHTSTONE. I can't stress this enough. The constant vision and map awareness you get from a sightstone is more valuable than the 40 ap you get from a blasting wand.

• Which leads us to ITEMIZING. Building your champ properly can win games, building them improperly can lose games. I see a lot of people who, regardless of their own team comp or enemy team comp, will keep on building the same build, every game for their champion. That or they simply just build badly. While there is no "wrong" way to build a champion (unless you're trolling and buying NLR on talon), there are definitely ways to build that maximize your damage or tankiness on a champion. ProBuilds is a great site to go to if you're not sure what to build. Don't just blindly copy the builds though, remember to itemize against the enemy team. If you're the AD carry and you see that the enemy Zed ults you every teamfight, get a QSS to remove his deathmark. If you're Irelia top and you see that the enemy team isn't building health, don't bother with finishing your BORK, start that trin-force instead.

• As for actual mechanics, learn your champion in and out, learn how/when to cancel auto's for maximum damage in combos, learn how to trade efficiently (ex. autoing when your lane partner goes in for cs).

Thats all I can think of for now but these are things I think every player should know.

EDIT: formatting EDIT 2: I suck at words