Two.
I think it's quite sad when parents don't bother with middle names, tbh. They're lovely for marking significant people and may make life easier if a child grows to really not like his/her first name - in some places/instances it can be easier to swap to calling oneself one's middle name instead.
My three dc all have two middle names, each of which has a connection of some kind to family member or friend, and all of which are additionally lovely names. I have one middle name. Dh has none, and a short first name at that. He couldn't care less but I do find it somehow sad.