LoL is 90% knowledge and 10% technical skill to be good. You can not improve if you do not know the champions: their skills, staves, cooldowns, damage, ratios, duration, controls, runes, objects, masteries, movement speeds, speed casting, attack speed, weave and initial magic resistance, damage, match-ups, optimized setups. You can not learn everything at once, you will do it as you go, but you can not cut it. Playing all the champions gives a very big LoL Boost.
Knowing how to build your champion is one of the most important skills in LoL. Champions are nothing without objects because your objects determine your abilities. Having unsuitable items means having unnecessary skills for the team (typically a tank that builds damage). Building your champion in LoL follows more or less the principle of Stone / Leaf / Scissors (as in 99% of games). The situation in the game, determines which objects you must build to counter the objects / champions of the opponent.
Learn the meta of objects,
