TFT Noob Question

So I just recently learned that in TFT there's a certain amount of champions thanks to this post in the pool, so you have to do your best not to have the same comp with another person.

Previously I always had thought of it as a card game where out of all the champions in league of legends you have a deck of cards where it's possible to at least 3-star each champion (so there are at least 9 cards per champion in every game). But now my small midget brain has been informed that for example in T1 there are 39 total champions. Can't be 39 cards because then that'd mean almost 5 cards for everyone. So I'm assuming total means champions.

But then that begs the question of how many cards per champions at least are there? Since T5 has 10 champions but while yes there's probability in play here, I never see more than 3 different champions so I'm starting to doubt and think that there are only 10 cards of T5 in a game.

Like for example: If there are 10 champions in T5, then what about different forms of Lux. Can there even be different Lux forms appearing in the game? And if so do they count as different champions cause they're a different form? [sg-lulu] I'm trying to dig into what's going on in TFT because I'm tired of seeing even last place having 3-star champions and I'm still sitting here with my 1 or 2-star squad T_T I blame my lack of knowledge for the reason why I'm hard stuck iron/bronze in TFT lmao I just wanna hit gold for TFT in a world where RNJesus has left the chat

##TLDR: I'm bad at TFT because I don't understand the bases of what makes the game. 1 how many cards (cards meaning 1-star champs) can you have in the TFT deck that's shared between everyone's shops? 2 do different Lux (and I guess Qiqi as well) elemental type count as a different champion? 3 does item drops have the same "formula" as the tier drops? Like there can only be a certain amount of B.F Sword in the game 4 my brain is too small so I forgot my next question so I guess this is it for now but I'm sorry if these questions have been answered already in different forums and my four eyes weren't enough to find it. So thank you for your help and have a good day