First, I think staying at Hamburg could be a perfectly fine option. Yes, the club is a dumpster fire, fighting off relegation for the third time in four years. But they are likely to remain in the top flight, and he's becoming an automatic starter for that team. Playing consistently against Bundesliga competition would be fine for his development.
Of course, it could be better. I see three places that could be good steps up: Hertha, Hoffenheim, and Köln. Neither Hertha nor Hoffenheim have a dominant striker at the moment, so Wood could contend as a starter. Köln have Modeste, but I imagine he'll be sold in the summer. Hoffenheim are solidly in the Champions League places, while Hertha and Köln are both contending for Europa League, so there will be a lot of squad rotation to keep players fresh. Finally, all three are professional and well-run. I'd be pretty ecstatic if he landed at any of those clubs.