I look at the preview first. Lets face it, if the preview isn't the greatest, you just don't sell your kit. I will look at the elements and if in small print I see "Not All Elements Shown" and there are only a few in the preview, I pass. This just tells me that the designer has not put 100% effort into it.
Second, I look for greenery if the kit has flowers. I have not yet came across a flower that doesn't have some sord of leaves LOL! I like to add flowers but the greenery will make those flowers pop.
Third, the addition of elements, ribbons, ric rac, buttons ... those are things that I look for. These days, clustering is big and if they don't have items like this, you just can't cluster.
Last, papers, I am not a paper lover but I like to see a selection of patterned and solids. That is my rant of what I look for in a kit.