By that, do you mean 'the people, the general public, all of us, the ordinary people' should be put, considered, first?'Populus prime' [prime is pronounced pree-may], because 'populus' means 'the people, people in general, the populace'' and 'prime' is the adverb formed from primus 'first'. ('Populus primus' would be taken to mean 'the first people') . I take it you want something meaning that the people are to go first or be considered first, above all, or the like, something involving a verb even if that's unstated, so the adverb is appropriate.