i am not speaking for everybody else, this is just from my experience:
i'm pretty new to league myself. i've been playing since may 2014, and i fell in love with the game pretty much lol
and i remember being afraid of ranked when i hit level 30 and decided that i should just put it off. but then on a whim, i decided to go solo. i finished, i think, 6 and 4. i was placed into silver ii.
ranked, imo, is nothing to be afraid of when you're starting off. it's a good way to see just how good you are yourself in the game. i think that you should go for it. don't treat the games like normals, though. your teammates and enemies are both trying to rank up (at least most of them), and it's a ladder that you have to climb; so the games are only going to get harder as you gain ELO
but before i post this reply, like, what i learned the hard way:
widen your champion pool a little bit. i think that you should main a role with a few champions (however, i think that one or two champs should be optimal) and you should know how to play every other role with one or two champions to a decent level. i mained jungle for so long that i forgot the other roles. also, when i did play normals for practice, i wasn't trying to see what i could improve on exactly. i just winged it to see results magically show up. i fricking ended season 4 as silver v with like a 19 and 30 record
however, now i know better, and once i feel very confident with playing this game again, i'll head back to ranked
ALSO, no, you can't queue with plats unless you're like a division below, i believe. (bronze can queue with silver, but not with gold; silver can queue with gold, but not with plat; et cetera [please correct me if i'm wrong]) also, even duoing with somebody of the same level, erm, you could say that it raises the difficulty.
Have fun on the rift, friend.
p.s.
watch the pros and learn from them if you want to (i recommend voyboy for mid/top, nightblue3 for jungle, krepo for support, and geranimo for adc)
if you find that there are people in ranked who refuse to positively communicate, just mute them and just continue playing to win (you'll still see each others' pings and positions, so that's enough. douse the flames. don't feed the trolls)
always think about what you can do better. don't blame your teammates too much. recognize their mistakes, yes, but think about how you could end up carrying the team or start calling shots as the support)
p.p.s.
set goals. my goal for season 5 is plat iii. :D i believe that i'm not bad at this game. i know what to do. i just need to start playing the game like it.
inb4 don't listen to this silver pleb
inb4 you can't inb4 yourself