Is expiation, along with making up the day, obligatory for one who intentionally experienced a wet dream during the daytime in Ramadan, and does not possess sufficient money to feed the needy?

Unless you are certain that semen has been discharged, your fast is valid and you are not required to make up for it.

If you are certain that semen has been discharged, then your fast is broken, and you are required to make up for it.

Expiation (kaffarah) is not obligatory for you, as it is only obligatory for breaking the fast through sexual intercourse.