Need nod advice for build

I like to make my own builds, but im quite new to poe and even with alot of reading I try to understand the mechanics, its hard to know, so I have a question regardning a few nods. (I playing a merc gas, explosive grenade build).

I have 14% increased fire pen without nods bellow. (Ive read you should be around 30 to 40% in pen)

Whats the better pick;

12% increased fire damage
21% fire penitration
15% duration on damaging aliment
30% increase ignite
30% increased damage against burning enemies

OR

Gain 8% as extra fire damage
Gain 8% as extra chaos damage
(time-lost diamond - stacking toxins and lasting toxins 2 nods)


The extra fire and chaos damage increased the dps alot more, but Im unsure about how much I gain with 21% increased penitration and the 30% increased damage agaisnt burning eniemis.