Edit: Anyone know where to get Giant Germ? I thought Kaiba used that card in the anime but I don't think it's listed as an unlock for his booster pack or duelist challenge.
Are the DLCs worth buying? how many of them are there?
If you buy the entirety of the DLC, you will be spending more money on the DLC than you did on the standalone game.
If there are particular cards you're looking for,
this google doc shows which pack you should buy.
I'm revisiting Yugioh after many years of not even looking at the series and sort of have gotten passionate about it. Beyond the typical, boring meta decks that take 10 minutes each to complete a turn, the game can be very fun when you play against a challenger that is using innovative strategies and it really shows the depth of the card game.
But if you're not passionate about Yugioh, I wouldn't recommend buying DLC because it'll just enable Konami for future games. They're already doing a shitty job by firing Kojima (MGS franchise) and Yugioh may be one of the very few other things they have left that people actually care about.
Though, I will give credit to Other Ocean. The AI in this game is extremely good and I've had a lot of fun completing duelist challenges. The campaign was more of just a grind but the duelist challenges are amazing.