In Magic: The Gathering, a "cube" refers to a custom-built set of cards assembled for drafting
Outside of those you have oldies that play like rock stars in Phytotitan
Let Mega Altaria ex absorb pressure first, then transition into controlled attacks once your board is stable
ZEXAL series, Gagaga XYZ has a few nifty weapons that can helpful for both new and experienced players
That being said, I don't have that same luxury with the more obscure decks so generally speaking, unless there's a lore specific reason of limiting cards to certain quantities due to their uniqueness (for example only 1 copy of each Crystal Beast existing), 2 or 3 copies are acceptable in order to preserve the feeling of the deck as it appeared in the anime
Contact: Jeremy 617-835-6562 or Paul 857-202-7873 Aug 9 MA, Woburn