As someone who's climbed from B3 to D2 (previously D1 before decay), I do agree with a lot of what you said. Also congratulations on reaching S2! However, I'd like to add some things on to what you've said/slightly alter some things.
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This is extremely true. However, there are certain scenarios where you kind of have to play a bit more aggressive early on in order to deny your opponent's early level 2 or reach your own. Playing too passive sometimes punishes you and allows your opponent to abuse said weakness (main case of this is bot lane's level 2 "powerspike" with certain champions like Leona, Blitzcrank, or mid lane's level 6) and it can be just a simple thing as being one or two creeps behind your enemy.
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Nothing else to really be said here, but keep in mind that there are times where you should peel of Dragon/Baron and either back off or fight the enemy team otherwise you'll end up losing a huge team fight due to the damage from the monster + enemy team. This is generally where Baron throws happen and everyone gets a good laugh at it when it happens in LCS.
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Nothing to say, good statement all around. Be supportive of your teammates if you can. Some people may just be having a bad day.
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Even after hundreds of ranked games, I still don't understand the surrendering early mentality. Death timers are long late game and almost anything can happen. Even if you seem to be losing at the time, always consider that even if it's a small chance, the entire enemy team can dc.
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Pick 2 roles and stick with them until you hit gold. This makes it so that you can focus on building two rune pages and understanding those champions even better. If you don't understand a champion, try playing that champion in a normal/bot game during free week to learn their strengths, weaknesses, and even cooldowns. It'll help a lot.
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Alright...Recommended items are decent for most champions, however, not all champions follow the cookie cutter builds that Riot gives. Keep in mind - EVERY GAME IS SITUATIONAL. I cannot stress this enough. As an ADC, there are some games where the enemy has a lot of CC or has CC that can punish you heavily. These are games where you want QSS. Games against a team without hard CC/minimal CC, you can get away with just buying a Bloodthirster. If you're against an AP heavy team, Hexdrinker is an amazing item to have. Sometimes building a Randuins can be justified against a heavy AD team. Remember - GA is a good hybrid defensive item, but if you feel that your team cannot aid you even if you revive again, it might be better to just go for more damage or a different defensive item.
As a support, if the enemy AP champion is fed, rush Aegis. Enemy has Ashe/Sona/Lissandra that can pick off your ADC with ult? Get a Mikaels to save your adc. Frozen Heart is a good item, don't get me wrong, but most of the time you're better off getting Randuin's Omen. It gives HP, good amount of Armor, and the active slow is amazing at peeling. Keep in mind, just because you're the support, it doesn't mean you can't go for the more self-defensive items. Once you have your core helper items (be it Locket, Mikaels, Randuins/FH), if you feel that you're getting bursted way too fast, you can build a Spirit Visage, Banshee's Veil, or Randuin's for yourself. A dead support isn't providing anything for the team.
As a tank, if you're against heavy AD, go Randuins/Sunfire/Dead Mans/Thornmail/Ninja Tabi. Heavy AP, go Spirit Visage/Banshee's Veil/Merc Treads. Mixture of both? Assess how the game is going. If the team is primarily AP/has a lot of CC, go with Visage and Merc Treads first, build an armor item for the adc, then go for Banshees or even zz'rot. Vice versa is rather similar. Sunfire/Tabi is good to build early. Randuin's is good mid/late game. Thornmail is good later into the game where you have decent HP to support the item's passive. Warmogs is recommended on a lot of champions. Keep in mind that it's passive does not kick in until you have 3k HP. The amount of people I see building it before then is honestly sad. HP also does not mean much if you don't have defensive stats to back it up. Always keep in mind what you're facing and adjust your build accordingly to who you think will be doing the most damage to you.
I feel that a lot of Mages shouldn't follow the recommended items list purely because of Athene's Unholy Grail. It gives 40 AP now, and while it does give decent mana regen, 20% CDR, and some AP, IT IS NOT WORTH BUYING IT ON SOME CHAMPIONS. You're better off purchasing Morellonomicon if you'd like the Mana/CDR. Abyssal Sceptor is good vs enemy AP champions especially against people like Le Blanc/Katarina who thrive on abusing your low MR. Against someone like Zed and Talon, getting an Seeker's Armguard early is always a good choice. Sometimes you might not even need to finish the Zhonyas, but the extra armor can be the difference between you living and killing your opponent and dying.
I can't quite speak for bruisers/assassin builds since I don't play many of them myself so I have yet to see the recommended item builds for them, but I do assume there are some things on the recommended items list that are out of date.
8 . Finally! Warding is important, but so is knowing WHERE to ward. Sometimes the ward in the bush is not always the best place to put it. Choke points (such as the area near blue buff, the small area outside of the raptor camp, etc.) are generally good places since it gives you more vision than you would obtain otherwise by putting the ward directly into the bush. There are several warding guides out there that can help you out. Always keep your eyes open though. Just because a ward is there doesn't mean that it'll keep the jungler away. Map awareness is key in this game. If you see the enemy jungler somewhere on the map, ping him so that your team knows where he's at so they can play around his positioning. The same can be said with mid laners if they seem to roam a lot.
A couple one final tip:
Since Riot has been kind enough to allow us to "ping" timers on spells, make sure you do! This is especially helpful if you have Teleport, Exhaust, Heal, an engage ult (Sona Crescendo, Kennen's Slicing Maelstorm, Hecarim's Onslaught of Shadows, etc.), Globals (Ashe's Crystal Arrow, TF's Destiny), or even more defensive ultimates (Janna's Monsoon, Soraka's Wish, Lissandra's Ice Tomb...thing). This helps your team coordinate a lot better and play around your abilities. Pinging Dragon/Baron timers when it's about 1 minute before spawning can also aid your team in setting up for objectives.
Anyways, sorry for the long post and good luck on the rift~
and sometimes 
in ranked and im trying to find some more champions like them
,champs like these, on people who can play them, regularly stomp in low elo even though they suck at high elo.
