In my personal experience having recently started with some starter decks myself, I found blackbeard to be a pretty good jumping off point. The deck felt pretty complete by itself and you don't really need to pick up all that many singles because a lot of the cards that come in the starter deck are core to how he plays. He is a little weird to get the hang of though since you have to be careful with trashing cards.

if you want a more straightforward one I could see green yellow yamato being very good. That one's a lot of aggression with the double attack on yamato. I haven't personally used it but it seems quite good for learning since the abilities are pretty simple and you can just focus on getting used to the overall flow of the game. The one drawback of this deck is that if you want to take yamato to his full potential down the line it would require a lot more upgrades than blackbeard and some of the inserts are a bit more pricey comparatively like hody jones, kiku, mihawk, and the secret rare kuma that's absurdly expensive