What would you recommend as the most important assets to get as the foundation to making a game?
TL;DR: Models > Gens > Environments > Hair > Clothes/Props/Poses should be the priority.
When it comes to Daz assets, try them before you buy them. Always. The PAs do a good job of promoting the bright spots and hiding the not-so-bright stuff. Non-Figure related things you might want: ManFriday's RenderQueue, MeshGrabber, Look at Me, Scene Optimizer and Ultimate Skin Manager (for the lazy) by the same PA.
Models/figure (as no_name already touched on. Colm Jackson, Bluejaunte(sp?), Victoria 8/8.1, Mousso, are pretty good places to start.) > genitalia (NGV8 work on almost every figure, but not all Daz figures come with gens. Dicktator/XY are comparable, just use whichever looks better to you.) > Environments (Fugazi1968/Ironman are bar-non the best on the Daz store. Stonemason, too, just make sure you have a rig capable of using it. Tesla3dcorp and Polish are hard to go wrong with as well. TruForm (on Renderosity.) has a lot of great stuff, as well. Again, need a beefier rig for his stuff.) > Hair (outoftouch, AprilYSH, WindField, and Rarestone/Nirvana stuff if you can find it are nice (Rarestone is Ravenstone now, iirc, and no longer on the Daz store. I believe she's on Renderosity.) as well. Propschick has some decent hairs too. > Clothes/Props/Poses (Hard to go wrong with clothes on the Daz store. They're all pretty good when it comes to the newer stuff. You'll gather props with the more environments you get, and poses are tricky. You can do them all yourself, but it can take a while. Zeddicus's poses are the only one's I'd really buy, though I use
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and
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a fair bit.)
You're going to run across these one-click packages that do all the lighting for you (somewhat), and while there's nothing inherently wrong with them, you're better off learning how to manually light scenes in Daz via Spotlights, Pointlights, and Emissives before you start using the aforementioned packages. You'll have far more control over the lighting, and the knowledge of knowing what lights and what style of lighting will look best for the scene. I will recommend
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, though. Makes your life easier for bigger scenes with lots of small lights, or even godrays.
As far as animations go, there are premade ones (Stimuli and AnimArts), but they aren't exactly cheap (specifically AnimArts) and in the former's case, overused. You're better off looking at some tutorials and see if you can get your head around it. But as mentioned, it's a whole different beast, especially with Daz. Learn the tool itself, and then come back to animation later.