Bassicly ranked games are way harder than normal also it provides you a rank. the only rule that riot has given to join ranked games is to be 30 and have more than 16 champions. but i would suggest you not go by then and i'll explain later why. let me explain you the categorys.
bronze (the very bottom):
People who start playing ranked games imedeiatlly end up there and its kinda hell, people expect you playing like a pro meanwhile they can't move on their own foot. Just don't go there.
silver (bottom but a litile bit higher)
you gonna find shit players there like bronze but sometimes you will see some guys trying and doing smth different generally trying to win with the right way. they know some more about lol but they still missing mechanics and exprience
gold (the middle category)
people would say that its good elo there you have fun. i totally dissagree its the worst elo by far get fast away from it. players there watching streams non-stop and try to accomplise things streamers do and thats a double edge sword, if they have some luck they will sucssed but mostly of times they fail and thats why you lose the game. also their attritube is by far the worse, they will flame you for like nothing same shit us a bronze
platinum (the good players not)
well platinium is okay place if you go higher than plat iii downstairs is a hell. people play kinda good they know some shit about the game there are feeders & flamers but for sure less than the bottom cattegorys.
diamond
same us platinium just people flame way less and sometimes games so easy becouse they know how to end the games.
i said that i am suggest you to not go in rankeds before you get some experience becuz you will endup in bronze, you will develop a logic that everyone else is failing and dragging down (whitch is not false, but its not the right mindset to go higher and be more good at the game && more fun) so play more normals learn about the game develop your mechanics on your fav champion and then go to ranked
The explainations from the categorys are my personal expierence