I've realised that all you gotta do to win outsmart people. This applies to 1v9 carrying, this applies to 1v1 in a lane. I have a problem, I am stupid, my IQ is 3 so I get outsmarted by everyone. The only thing I know how to do is learn how to carry but I am not smart enough to actually do it. So what in game items do I buy to increase my champs IQ stats?
First of all, work on getting rid of that "its me against the world" mentality. "All you gotta do to win is outsmart people" where do you gather that? Yes, League of legends has A LOT to do with psychology, prediction and intelligence - but that's not all of it.
You need a plan, you need preparation and you need knowledge.
You ask for what items you should buy.
First of all, items will vary with nearly every game - because you need to adapt your items to the players on the other team. But there are a couple general guidelines here. Ask if you want me to teach you them in a separate comment.
Secondly, you did not actually list any champions you play. That would be a good start, so that players like me can work on item suggestions for you. Please tell me the names of some of the champions you like to play the most, and where you usually play them. Feel free to list champions you have a hard time playing against too, if you want to hear some advice on what you can do to play against them.
So first of all: master your champion. Learn what they can do, how to do it and practice actually doing it. Make sure you know the range of your spells, how long their cooldowns are, how fast you run out of resources from using them and how much damage it does / healing it provides / crowd control it can cause / et cetera.
Secondly: play your champion against various opponents. Dont give up when you lose. Learn from experience - advice and theory will only help prepare you for what might happen during a match, it will not teach you how to react to situations you could'nt possibly have expected.
Third: learn from other players. Had a great player on your team, or a super fed monster on the opposing team? Try to remember what they did and see if you can mix that into your own playstyle. Do NOT attempt to copy them - using their item builds, masteries or runes will usually not work for you as well as it does for them.
Four: dont get angry. Dont write. Dont give up.*
*Dont give up: this does not mean never surrender. If the enemy team has 20 kills and one of your inhibitors down at 8 minutes, giving up is not shameful.
Even if you think a match is lost, dont actually stop playing. Detach yourself - as in, dont focus so hard on the match. If you think to yourself "This match is lost anyway, i might as well see what i can do before they win" then you wont actually care so much about the loss itself.
Dont get too invested in your matches. Depending on your deciation, you may play hundreds of games in a month. The result of each individual match does not matter that much in the long run. Always play to win, but dont get upset or think too much about it when you lose. Okay, you did what you could that match. On to the next one.
If you do get angry: take a break. Do something else, play another game for a couple days. Stay away from league until you want to play without getting angry again.
Five: learn to pay attention to your teammates. This does NOT mean read and respond to everything they say in the chat. If a teammate is writing a lot, mute them and focus on playing. But watch where your teammates are, and what they do. Try to play alongside them - even if you cant beat that Fiora on your own, chances are she will still die when your mid lane Galio drops out of the sky to back you up.
Six: pay attention to your opponents. Try to watch where they are, and what items they buy. Use your trinket - ward in places that can help you spot enemies, such as the bushes in the middle of the river or the Y-shaped bushes near top and bot lane.
Does that Jayce/Caitlyn/Ahri love to repeatedly pop in and out of bushes to basic attack you? Plant a ward in the bush so that minions will focus them when they do.
I'll stop here with a lucky seven: Ask. Ask questions, ask for help, and BE PATIENT when you recieve responses. There are a lot of negative players in this community, but a lot of nice people too. Be patient even if the response you recieve is not something you like hearing.
Now, back to the top of this comment and follow my suggestions there.
yes
books, duh
the optimal build is
with the sixth slot optionally or 
too many trash players in soloque
