As @XandeRoot suggests, your dedicated 1h ranged chaos options generally better support Pyromancer than Deceiver, with the big archetype here being Darkblaze Pyromancer, e.g.
so playing elemental is certainly worth exploring if you’re really set on a Deceiver with two guns.
If you’re willing to play 2h ranged instead, something like
is worth looking into if you can get together the gear. (You can always choose a rifle illusion for the crossbow if you want to stick to the theme of guns.)
In any case, for leveling, you may actually find that you have a more pleasant experience playing chaos caster than chaos ranged using Bloodsworn Scepter and Abaddoth’s Sermons rather than guns, and if you really end up liking that playstyle, you can build towards something like this:
EDIT: here’s a beginner guide for chaos caster Pyromancer as well on the off-chance that you find yourself looking for beginner Pyromancer guides: