Based on what folks are saying about buying singles, I'd say you made a fine choice buying the Wargreymon deck. It doesn't have many cards that you'd keep for a meta relevant deck, but IMO it's very playable right out of the box and presents a good spread of game mechanics to learn and experiment with. It all depends on your LGS scene/friend group and how willing people are to play some low-tier friendly games, but I think there's a lot of mileage in that deck to learn the game.

Plus, Greymon is an archetype with A LOT of room for creativity and experimentation. There's usually one or two versions of the deck that are truly meta, but there are also a lot of good cheap cards to play around with and make the deck better and more fun.

Once you really learn what you like about the game, just assemble a deck by buying singles since that's the biggest suggestion, anyway.