Hi there, I'm Naturesbf. I've been around the scene for as long as it's existed, pretty much always Challenger but sometimes I take a break and let myself decay. I'm someone that is really into making small optimizations everywhere I can - it's fun to me, and if you do it enough it ends up having a large impact.
Because of this I always try and make sure to understand the current systems in the game to the best of my ability to see how to optimize playing around them, and systems are something that the community is very often misinformed or under informed about. I'm going to explain how some of the hidden systems work, and give some ways to use that knowledge to your advantage.
Disclaimer: Most things I am talking about I am completely certain about, whether from my own testing, from statements from Riot, or from discussion in Lobby2, but a couple mechanics are incredibly time consuming to test to figure out and I feel pretty sure about it but not certain. I will tell you which those are when they come up.
The 'Guaranteed Chosen' System
When you are offered chosens is not completely random - there are a few rules that the game follows and it is strict on these rules, causing you to be 'guaranteed' a certain number of chosens in your shops.
First of all, you are guaranteed a chosen by stage 2-2. So, on either stage 1-3, 1-4, 2-1, or 2-2, you WILL be offered a chosen, possibly multiple.
An easy way to use this to your advantage is to prelevel on 1-4 if you haven't been offered a chosen yet, in order to give yourself a chance at a $2 chosen on 2-1 or 2-2 (this logic still holds up if it's 2-1 and you haven't leveled yet and still haven't seen a chosen, as you know for sure you will get a chosen next round).
Secondly, you are guaranteed to be offered three chosens per stage if you have not owned a chosen at any point during the stage. No, this does not only apply in Stage 2, this is still the case in stage 7 if somehow the game lasted that long and you somehow don't have a chosen.
Because of this, preleveling on X-3 rounds (2-3, 3-3, 4-3) to levels 5, 6/7, 8 respectively becomes a lot better if you do not have chosens yet and haven't been offered them on that stage yet. On stage 2-3, you definitely have already been offered one, as stage 1 and stage 2 count as a single stage and we learned already that 2-2 is the latest you can be offered your first chosen. However, some games you actually may not have a chosen during the early parts of stage 3 for whatever reason, maybe you are lose streaking or something, and preleveling on 3-3 becomes a lot more valuable as you are guaranteed a chosen on 3-5, 3-6, and 3-7.
Note that this still applies even if you rolled earlier in the round - if you rolled on 3-2, and saw two chosens, and it is now 3-6 and you have been offered 0 other chosens, you are guaranteed a chosen on 3-7.
Now for something a bit weird... You can technically manipulate exactly when you are offered these chosens. It's just usually very impractical.
Once the round is X-7, the game doesn't actually differentiate between natural shops and rerolls for the purpose of guaranteed chosens. Thus, if you were to lock your shop and deny the opportunity for yourself to be offered chosens, and then rerolled on stage X-7, every reroll you did would have a chosen in it until you had met your 3 chosens per stage guarantee.
I think this is something that has VERY niche use cases and I would guess that over 99% of the Challenger community has/had no idea that that is even possible, so feel free to ignore it completely if you'd like.
The one way I see it being used is if you are someone, like me, that is willing to full open fort stage 2 some games and then play flexibly after the fact.
If you have a large gold start, but your board is bad, and thus full open forting is a decent play, then you can lock your shop starting on stage 1-4 or 2-1 all the way until 2-7. Then, on 2-7, you go level 6 (because you are rich), and roll exactly 3 times (or until you hit a good chosen), giving yourself a massive powerspike and setting up to try and winstreak through stage 3.
Note about the previous paragraph about playing that situation optimally... If you have a 12 gold start you should be 58 gold on 2-6 AKA 50g level 5 and thus I don't think it's correct to lock on that turn, just take one level 5 shop and 2 level 6 shops. You will be 43g level 6 on 2-7, 39g after rolling twice, then you can spend (19g+any gold drops) to make a decent team from a level 5 shop, and three level 6 shops counting 3-1, and be 30g level 6 on 3-1.
The Matchmaking System
One of my biggest pet peeves is reading people say 'matchmaking resets' when a player dies, and it happens ALL. THE. TIME. On Reddit, in Twitch chat, whatever. It's a giant misconception in the TFT community, and even the TFTHub website people use has it set to reset when a player dies.
It doesn't. Let me explain how matchmaking works (until it's inevitably changed, but players have known about it for a year and it hasn't been changed yet so maybe not).
First of all, while 8 players are alive, you cannot face the same player twice within 5 rounds. In practice, this means that once 5 rounds have passed, you will be limited to 3 players you can potentially face and can position purely for them.
When a player dies, that '5' counter goes down by 1. At 7 players alive, you cannot face the same player twice within 4 rounds. 6 players alive, 3 rounds. At 5 players, you would think it's 2 rounds, but I am pretty sure it stays at 3 rounds and due to the ghost being a possible opponent it isn't a problem. More on the ghost later.
At 4 players alive, you can throw the earlier info out and just know that it's round robin. You won't face the exact same player you fought when there were 5 alive the turn before, either.
Once there are 3 players alive, THERE IS A RESET. My guess is that this isn't actually programmed as a 'reset', because it's the ONLY time there is a reset, but rather the algorithm just causes there to be one.
You can actually face the exact same player three times in a row at this stage in the game. On the final round with 4 players alive, you face a player. The next round, you face either the ghost of that player, or the player himself again since it reset. On the third round, you face whichever you did not face on the second round. So if there's some guy with a Yone 3 and you face him 3 times in a row... Get player diff'd.
3 players alive works like this... Lets assume you are against P1 and P2, and the first round of Final 3 you go against P1 (you could also go against P2 or a ghost). The next round, you will go against either P2 or a ghost (of either P1 or P2). The round after that, you will go against either P2 or a ghost (again, of either P1 or P2, you CAN face the same ghost you fought before). From then on, you will stay in that exact order for the rest of Final 3, and I am pretty sure which ghost you are against will swap every time you face the ghost. So, for example, this is how a Final 3 could go.
Round 1 Opponent: P1
Round 2 Opponent: Ghost of P1/P2
Round 3 Opponent: P2
Round 4 Opponent: P1
Round 5 Opponent: Ghost of P1/2 (Same OR different as Round 2)
Round 6 Opponent: P2
Repeat until someone dies
Now, how ghosts work. Almost everything I am writing for ghosts I am only pretty sure on. Ghosts seem to act as an extra player themselves. They DEFINITELY do not act as the player you are facing against for the purpose of matchmaking, they act as their own entity. This means that if you face a ghost, just know that you won't face one again for X number of rounds depending on how many are alive, but you could totally still face the player that the ghost was representing. In terms of choosing which player the ghost represents... this seems to be completely random.
Do note that at 7 players alive, the ghost doesn't increase the player count to 8 for the purpose of matchmaking - as stated before, at 7 alive you cannot face the same player twice within 4 rounds, unlike at 8 alive where it's 5 rounds.
The Item Dropping System
This system certainly has the least information on it if you look around, and many I believe know that something like it exists, and thus they play around it, but they don't know the specifics of how it works.
It's pretty simple: Every time there is a carousel, you add 1 of each of the 8 items to a 'bag', and those are the potential items that can drop for you.
That's it. Starting at the stage 1-1 carousel, you will have 8 items added to the bag. One tear, one rod, one sword, one bow, one vest, one belt, one cloak, and one pair of gloves. This means that at stage 2-1, the only possible way for you to have two of the same item is if you took it from the carousel, as these items in the bag ONLY count for items that are dropped from neutral mobs. Then, at the stage 2-4 carousel, one of each item gets added again, without removing the previous ones (so, if you got one tear but no vests from stage 1 neutrals, you will now have one tear and two vests in the bag). This means it is twice as likely for you to get an item dropped that you haven't had dropped yet, compared to an item that has already been dropped, when you are at the stage 2 neutrals.
Also, a few patches ago, the stage 4 carousel stopped adding an item to the bag, meaning you can only be dropped three of a specific item anymore.
You typically, and at a minimum, get 12 items per game not counting fortune or lantern rewards. Four of these are from carousels, so you are usually dropped eight. This means that you will on average get one of each item per game naturally, and thus if you are trying to get absolute perfect items for some specific unit or comp, you should be taking items at carousels that you will need multiple of. Also, importantly, the very first carousel you should always take an item that you will feel okay having at least two of throughout the game, and maybe even on 2-1.
Some extra tidbits of info... Spatulas do not count as items for the purpose of your minimum/maximum item count, they are a bonus. Neekos also do not lose you items, they lose you gold (2-4 gold per Neeko unless they are from a rare box).
That's all for now. As TFT gets updated more, and systems are changed and added, I will continue to try and understand them as best as I can and explain them as best as I can, as the advantages that come from understanding these systems can be massive.