The card game in Final Fantasy VIII was a pretty huge success I think which caused Square to stick a card game into Final Fantasy IX as well. But they didn't want to just do the same old thing so they added all kinds of crazy things to the mini game. Rather than have 4 directions of influence they added in diagonals to make it 8 directional. They made it so each card didn't necessarily work in every direction, instead it would have some combination of the 8 directions. They gave cards an attack value, a physical defense value, and a magic attack value. They made different cards attack physical or magical based on what the card represents. They added in a random component so even a weak card could sometimes beat a strong card. And they let the cards level up and get more powerful as you used them. They also removed pretty much any benefit you could get from playing the game. FFVIII had tons of powerful stuff you could make out of cards. FFIX has pretty much no reason to play the game other than the fun of playing it or the OCD need to 'catch them all'.
For the most part from the things I've read and the people I talked to about these games back in the day the changes were, by and large, a flop. The FFVIII card game was awesome and I can't remember talking to someone who hated it. But the changes in FFIX tended to remove player control from the game. You can't see your opponent's hand and sometimes you just lose to random chance. This is bad for the player because games are played for ante and while the computer can just restock and doesn't mind losing something leveled up the player can't just restock and certainly minds losing a card they've invested a lot of time into leveling. The computer will tend to use the cards they win so you can win them back, but you did lose with your best card... Your odds have to be worse with your opponent having it instead of you.
The randomness can be frustrating, so I don't know if I'm going to stick it out, but I'm going to try to build a maxxed out collection. There's a collector level in the game that awards you points based on owning cards with certain criteria and there is an absolute maximum level you can reach. It involves owning exactly one copy of each of the 100 cards in the game. Each of those cards needs to have a unique combination of the 8 possible directions (there are 2^8=256 such combinations and you can save/reload before earning a card to cause it to spawn with a new random combination) and each of them also needs to be leveled up to the maximum attack type. Each card has a 1.56% chance after each fight of upgrading from the starting attack type to attack type X and each X card has a .56% chance after each fight of upgrading from X to A. That's a lot of card battles... Especially since you'll need to be winning fights with some low level cards in order to level them up. But I think I'm up for the task! Maybe!
The most important thing to start with is making sure I can actually get my hand on one copy of every card. I certainly remember from playing before that some cards can only be found in one spot or in ante from one opponent and I need to make sure I don't miss any of them. I couldn't find an immediate list of cards that might be missed but I did find a list of locations for every card in the game. So I decided to go through that list and make note of anything I need to make sure I don't miss. Lots of cards, especially the low level stuff, can be won in random encounters or can be trivially won in a card battle so I don't need to worry about them at all.
It looks from the list like a lot of stuff can actually be won from guys in the card arena on disk 4. I'm going to assert that guys like Beast Master Gilbert is actually able to be fought many times to pay out the large number of seemingly rare cards he owns and therefore not worry about them. If that turns out to not be true, oh well, and I will learn for next time!
Here's what I do need to worry about:
Namingway card is the only one that can't be won in a card battle on disk 4. You can win it from Mario in the card tournament on disk 3, or you can find it in the desert palace/sanctum on disk 3.
Wow. I hope this card list is right. It feels so strange that you can just go and card battle dudes to win basically every card in the game. This certainly wasn't the case in FFVIII! I guess that's probably because the unique cards in that game could be converted into powerful items and here they're not worth anything at all except having them?
I'm a little worried there's something wrong with this card list but it would explain why I couldn't find a list of missable cards anywhere and why the only card really called out in the 'do absolutely everything' FAQ was Namingwary.
Oh, and on a side note... Apparently some German company actually made a board game version of Tetra Master! The BGG comments make it sound pretty bad, but I still have this urge to try to track it down...