It will be impossible to get Milotic. The berries you can find in the wild don't have a good enough beauty to sheen ratio, and your Feebas would get full before its beauty stat is high enough to evolve. The berries needed to evolve Feebas are received from the Berry Master or by talking to Kiri in Sootopolis. The problem is that they give you berries 'once a day.' So not only will your berries not grow, if you could get them, but you can't even get them in the first place, because it's a daily event.
only less than nothing, as nothing could have equaled you
https://i.ibb.co/5skW2Jq/Mado2.png