I’ve talked to several different priests about my discernment process. From a general standpoint from what I’ve heard and read, studying ancient philosophy and theology are both required and a good idea for those considering the priesthood. These topics will you understand more about your personal faith while also learning more about the world. I hope this helps. Remember though, the priesthood isn’t something we choose to go into, it is something we are called to.
John 15:16 “You did not choose me, but I chose you and appointed you that you should go and bear fruit and that your fruit should abide; so that whatever you ask the Father in my name, he may give it to you.”