It´s the same as every other game you play in a ranked mode. You can´t control everything! It´s simply not in your hand. But you gotta deal with it. That will set you apart from others, if you are good.
If you play 5v5 on Summoner´s Rift, you control 20% of the game. You can impact others, but you get my point. Now, if you play well more often then you play bad, you will rank up. Until the point when you are where you belong and end up at 50%. I played 3 seasons and for some reason, I get placed bronze everytime (b5, b5, b3). But 1 week later I´m silver, simply because I don´t belong there. It takes me a bit longer, but I´ll get out of silver too. I´m gold, that is where I belong. There I have good games and bad games, but I don´t dominate anymore. It doesn´t matter if I get bad or good teammates, I´ll get out of bronze and silver anyway.
It will be the same in TFT. You might have super unlucky games: you can´t get that one unit you need, creeps don´t drop items, someone took the champ you wanted in the carousel. Happens. It won´t happen everytime. And it happens for the others too. But how you handle it, how flexible you are with what you got will show your skill.
Sorry if this insults you, but you seem to be a "I´m in elo hell"-person. You are so focused on the luck/bad luck aspect of the game, that´s like an excuse. Getting third consistantly is not that hard, even with bad luck. If you have the skills, you´ll get there often enough to rank up. Simple. The more games you play, the more accurate these systems are and the better your skill gets represented by a rank.
