Guardian gearing question

I recently switched from boomkin to guardian. Which I have played feral wrath-cata. And now am wanting to tank again. But I have 0 pve guardian gear, I have full pvp gear... and for doing just heroics would that be alright to tank in? even with pvp gems and enchants. Or would I be better off buying the best grens I can and starting with that? but still using my polearm?

thanks :)