Hi, I'm Qialex. My main account is Charlie Sheen v3 on the EUNE Server (1500 Elo season 2, Diamond 3 Season 3, over 3k Games in normal, around 600 in ranked total.), my main roles are Mid and top, which also happened to be the easiest roles to carry with in low elo because of high snowball potential. I made this guide to help people jump into ranked without suffering the consequence of getting stuck in Bronze because they went into ranked unprepared which often lead to losing interest / getting mad at this game.
I am going to categorize my guide into runes, masteries, roles, popular champions, items, matchups and tips.
Without further blabbering, lets get started.

First of all, congratulations to making it to level 30, it's been a tough road filled with flamers, trolls, smurfs and well, more smurfs.
Now you're level 30, you can jump straight into ranked, where everyone is friendly, teamwork is a virtue and GG is said at the end of every game!
Hah, if you actually believed that for even a split second I suggest you uninstalling the game.
First things first, mindset.
Have the mindset of playing every game 1v9 (Your team WILL help their team more by feeding and flaming you than actually helping you), and have the mindset of ''You're a beast, you can carry this ****.'' You have to have tough skin because people WILL flame you at every, single, divison. While there ARE really nice and friendly people, most of the people will be toxic **********ers, so you have to be prepared for them.
Don't be afraid of losing, even the best of us loses once in a while. However, if you're feeling like you're tilted after a losestreak, or just when you're having a losestreak in general, don't play more games until you feel better / you start doing things differently, e.g. different music genre, different duoq partners and so on.

LEARN FROM YOUR LOSES, LEARN FROM YOUR VICTORIES:
Most of your loses will be ''because of your team trolled too much / too hard to carry'', or at least that will be the mentality of 95% of the players, sometimes it's true, but do remember that there are ALWAYS room for improvements, no matter how WELL you do or how BAD you do there's always a reason and you can always improve. Watch your replays, watch how they beat you or how you beat them, watch how you won the teamfight or lost the baron. Remember every good play, remember every bad mistake. Improve.

Ah, runes.
Never, NEVER go into a ranked game without a full and functioning tier 3 runepage, you will be put at a distinct disadvantage without a full runepage that suits your champion, no matter how good of a player you are runes will put you into a bad spot, and even if you win your matchup remember that you can do that five times easier WITH runes.

On the road to 30 you should have enough IP for a handful of champions and runes, never buy tier 1 and tier 2 runepages, you can get a few just to help out but never build a full page with them. Tier 3 or bust.

I will post few standard rune pages that are almost good for any situration:

Standard mid AP : Magic Pen Reds, Armor Yellows, Flat / lvl MR blues and AP Quints.
The most standard and versatile runes for any champion that scales with AP and deals mostly magical damage. (Role: Ap junglers, ap mid, ap top, aggressive ap support)

Standard AD: AD Reds, Armor Yellows, flat/lvl MR blues and AD quints.
Standard ad runes aiming to maximize your early game, because most of the ad champions scale well with items. (Role: Ad top, Ad mid, Ad junglers, aggressive nuking ADCs)

Standard ADC: Same runes as standard AD but with lifesteal quints x2 and AD x1 instead of AD x3.

Standard roamers: Same runes as standard AD/AP, but instead put Movement speed in the quints. (Roles: Roaming Junglers and Mids, Singed.)

Standard support: Hybrid Pen Reds, Armor yellows, cdr / mr / mrlvl blues and gold per 5 quints.

Dunno how to post the masteries on this page, halp pls.
(Lolking has much easier mastery pages :c)

Mid is THE role.
It is the role with the most room to make plays, the role that carries the hardest, the role that arguably requires most skills and the role that everyone in soloq will instantly lock for.
In mid your job is to either:
a) Push your lane hard, farm jungle, push your lane hard, farm jungle, get 300 cs at 25 minutes and wreck faces with your 4 completed items. (Good if you scale harder than their mid and you your roam isn't as strong as theirs)
b) Roam the map so hard that they will be terrified to sit at their own turrets and starts to flame their mid for not following. (Good if you're a assassin with good roam, if roamed successfully you can shut down 2 or 3 lanes)
c) If you know their mid is going to do more in teamfights, shut their mid down while forcing small fights instead of big teamfights, split pushing, grabbing objectives and applying map pressure. (Good for winning the game early leaving little room for throws)

Your goal on mid:
Push. Roam. Assassinate. Apply pressure to the map.

Here's few champions that I recommend for every role.
Mid:
Orianna: Takes a bit of mechanical skill to get used to, but a very safe pick, a lot of burst but has sustained damage once you get some cdr, works with any team comp and a top mid pick at any level.
Forces you to learn teamfighting timing and targeting.

Fizz: Almost ALWAYS banned, but a very snowbally champion. A bit hard to control because of him being melee but once you get his damage output down you can easily all in someone and snowball from there.
Forces you to learn the art of dives and all ins and roaming.

Ahri: Recently changed into a one-skillshot-wonder, either you hit her charm and instantly gib people or you don't.
Forces you to learn landing clutch skillshots, roaming, blink positioning and comboing.

Nidalee: A high damage, high poking and annoying as hell champion, has two forms, one for seiging and poking, the other finishes high priority targets off while being a mobile cat. Forces you to learn how to land skillshots, when and how to roam, when to go into melee range and when to safely poke.

Karthus: Safe farmer, crazy lategame, global ultimate and able to keep casting spells while dead.
Forces you to learn how to farm with a champion that is very squishy early game, skillshots with your skittles, teamfight placement with your passive and defile AOE, map awareness with your ult timing.

Top is the arguably most selfish lane, there you're left all alone (Except for those pesky junglers) to duel, farm, proxy, push, do whatever you like man, you're top.
Top is the home for bruisers, farmers/lategame carries and very rarely, assassins.
Your job top is to outduel their top, survive ganks and push, push, push. You should always have the most farm due to the access to jungle, proxy farming and the fact that most mids roam bot, and you don't need to be bothered with dragon most of the time.
Most tops are late game monsters by being a huge wall in front of enemies team and dealing enough damage to be a threat to their MVPs.
Your goal on top:
Farm. Duel. Survive. Push. Teamfight.

Renekton: He's almost the definition of a beast top. Lane bully, hard farmer, in built sustain and teamfight monster.
Forces you to learn: All inning early, resource management, comboing and how to deal with getting kited.

Lee sin: This one's a personal favorite. He has very good early damage with fort pot start, he has overall decent scaling on all of his spells to be able to go heavy ad, he is VERY flashy and jumpy, his kit offers everything you need, gapcloser, execute, slow, AS slow, shield, ally shield and lifesteal. His ult is a HUGE playmaker once you know how to use it, whether it is for executing, peeling, aoe or kicking their MVP into your team. He is also a VERY effective counter jungler and roamer.
Forces you to learn: Energy management, Comboing, Positioning, Roaming and know how to survive the most extreme siturations.

Shen: Another personal favorite, a huge tank with the ability to teleport to ANY ally while applying a life saving shield to them. He has respectful damage even when building full tank and is a threat to any squishier targets with his burst. Great splitpusher due to being tanky, good damage to turrets, able to escape ganks and can help his team from anywhere, also a playmaker with his taunts.
Forces you to learn: How to play early game with a weak early game champion, how to farm without aoe, map awearness, positioning, decision making and teamfighting.

Kennen: He will win 90% of the his matchups in lane if played properly, he is the bane of all melee champions, top or not. His poke in lane combined with his ability to stunlock people with surprising burst makes him one of the best top picks.
Forces you to learn: Poking with autoattacks, csing while poking, combo, resource management, teamfighting and positioning.

Kha'Zix: Previously the dominant mid transforming bug is now better played top due to his waveclear nerf. He will hit like a TRUCK on isolated targets top even if they're tanks. He has very good burst once he gets ahead and he can assassinate targets easily lategame.
Forces you to learn: When to use spell, minion awareness (Knowing where the minions are and how he can isolate the champions by either zoning them or killing minions and instantly attacking them), roaming, assassination and reset management.