Don't be spiritual, be honest instead." It does not go well at all with the meaning of spirituality which has intellectual, moral and cultural values. It should be the other way: Don't be materialistic, be honest instead
"He is a spiritual person." It means: he has a higher level of consciousness. He can distinguish good from the bad. He can feel the presence of unique Atman or God within him
"I'm spiritual." It means: I have the knowledge of spirit, the all powerful Almighty or Atman.