I don’t think any kind of stuff could come first, be it matter or some sort of mind-stuff. What comes first in the sense of principle would be something like form or structure or mediation. (“First” in the general sense of principle is said in several ways, but I’m inclined to re-collapse some of them. These days, I consider ontology to be mostly either redundant with semantic and epistemological methodological senses, or else just a mistake. This leaves a long view of methodology as the best candidate for a principle.) The air of paradox associated with saying something like mediation comes first is dispelled if we recall that apparent immediacy is mediated immediacy. This just reflects the fact that methodologically, we are never at a completely pure beginning, and always start in medias res.
Mind especially seems to me not best approached as a kind of stuff at all. It is first and foremost a way of doing. Then, too, what is loosely called the “matter” that we care about in concrete cases often comes down to potentiality, or dispositions to respond in certain ways when acted upon (which is distinct from Aristotelian matter, as I understand it). Both of these are adverbial characterizations, though things of this sort can always be nominalized for convenient reference.
Aristotle suggests that what is first “for us” (the short view of methodology) is some sort of activity that we tentatively pick out within appearance. We then move forward by developing the adverbial characterization of that activity in terms of form or structure or mediation. (See also First Principles Come Last; Owl; Passive Synthesis, Active Sense; Realism, Idealism; Johnston’s Pippin.)