I don't think a pc can post without a gpu. Unless you didn't mention it in your posting.
Put together the cpu, mobo, cpu fan, ram & gpu. Hook it up to psu.
Does the fans & lights stay on while the pc is powered on? Just blank screen? Might be memory. Try each stick of ram in each of the slots. Once the pc posts, set up ram in bios. Probably the vdimm needs to be bumped up.