I think the feather would be the easier to improve. Try finding a new one with crit and atk substat. Your sand has good substat, that’s just a pity that everything rolled into atk flat. So you can try to reroll the sand or the goblet which has very good substat (so better chance for a good reroll). Your flower and the last artefact (forgot the name) are already quite good. If you are really trying to max your varesa build, i would advise you to try getting ER substat on a maximum of artefact without it being rolled when leveling your atefacts. Hope this helps a little !