The image sets are not in specific order. I usually group the images in three sets so they would span a row on my Instagram account. I then pick the ones I like the most as the first images in a set, while keeping composition and color coherence amongst the three images, thus forming a triptych.
Very generally speaking, the ones in front are images that I personally prefer the most, followed by images that I think are less successful. But I would never post anything that I don’t personally like, so I do like all of them. I also know that what’s considered good is highly subjective — often people respond strongly with images that I don’t like as much, and vice versa. So I try to be as objective as possible when I pick the images. I also try to pick images that are different from each other, so that they would form a coherent set.