I know that, it's not hard for him to turn on at all though. I would need only 4-5 creatures on the field for the god to be turned on. But once again I'm not too terribly worried about deicide like a mono blue player would be and I don't think it's worth splashing blue at all.

Have you thought about using Mana Confluence rather than Orzhov Guildgate ? With 11 one drops, some black and some white, it seems like having turn one mana of either colour could be a big boon, and losing a couple of life over the course of the game shouldn't be a big deal for a deck this aggressive.

Yeah, Mana Confluence is clearly better here. I will be sure to be picking up a playset (especially before shocklands rotate out)

And Mutavaults would also be great here as well but I don't want to spend $150 on a playset of them if they might rotate out. If they remain in standard I'll pick them up during M15 or Huey block.

Does orzhov charm work if Athreos isn't a creature yet? I really want to build an Athreos deck but I need a way to get around Deicide

Athreos does need to be a creature unfortunately but given this is an aggro deck I can't imagine that that is too much of a problem.