Which Yu-Gi-Oh booster box should I buy?

It would be easier on you to just buy all of the singles rather than rifling through boxes. Since your decks wont be legal, I and all the other experts on YA couldn't care less what deck you build because it wont matter in the long run. I would definitely recommend Invasion of Chaos or one of the older sets if you were just looking for collection cards. But because you are making a deck, it is easier and cheaper for you to go out and just buy the singles from Trollandtoad or ebay. Because your type of deck isn't popular, the cards will be cheap.