What is the ruling regarding the expiation for someone who swore not to engage in daydreams, then returned to them and swore again not to return unless it was conditional upon taking a ghusl afterward? Are these considered two separate oaths that necessitate two expiations?

These are two oaths: that you will not indulge in those dreams, and that you will perform ghusl (definition) if you do indulge in them. According to the majority of scholars, you are liable for two expiations (kaffarat) due to these two oaths, while the Hanbalis hold that one expiation suffices. The expiation for an oath is feeding ten poor persons, or clothing them, or freeing a slave. If you are unable to do any of these, then you must fast for three days. It is advisable to get rid of daydreams by occupying your thoughts with beneficial reflections concerning matters of religion and worldly affairs.