What are oprtimal support gems to link a fire trap with ?

Sorry for necrothreading and a bit OT, but I'm trying to build a fire trap shadow (OK, maybe not the wisest starting point) and I'm a bit confused about Searing Touch.
I have one, and /itemlevel says it's 63 - so I should be able to get 6 sockets on it, right? Problem is, even though I am not aiming for 6 sockets (I'd take them of course) and would be content with 4L, I can't seem to get more than 3 sockets on that thing.
Does my character level have anything to do with the maximum number of sockets, too?

I forgot what itemlevel u need for 6 sockets hmm...and as far as i remember char level what u asked,doesnt affect the rolls :D i think just item level affects chance to Sockets number/links number :D

I use this for my fire traps

Generally only use to protect my totems but they do blow stuff up nicely

I prefer 1 handed w/ shield for extra stats on the shield

Most important thing (IMHO) is using more than 1 trap to get around the cooldown

2 is good, 3 is overkill altho if you are making a build around firetrap i guess 3 would be good

Mikrotherion - ilvl 50 is needed for 6 socket, char lvl makes no difference so you will be able to 6 socket it. I've just done same as what you are trying on my chest. Used over 500 jewellers and still no 6 socket so settled for 5 and was very lucky with the fusings as i got it 5L within 20. Guess the RNG felt guilty :)

In this order (IMO)

Fire trap:
-conc effect
-fire pen
-chance to ign/ele profi (depending if you want to go for single or AoE dps)

I personally just use 3-link shield to house my conc eff, fire pen trap.

I built a very tanky witch a while back that primarily used EA as her offensive ability. Since I was heavily invested over in the Templar/marauder area, after so many passive points I had a strength stat that rivaled my intelligence.

I decided to try this 4L:
Fire Trap > Iron Will > Concentrated Effect > Fire Penetration

At level 72, I had only conc effect at max possible level, the others had a ways to catch up yet.

DPS of Fire Trap - 1555

Fire penetration gem (only lvl 10 so far T_T) -> -26% fire resist
primary curse (for use with EA) - Flammability -49% fire resist
passive keystone Elemental Equilibrium -> -50% fire resist

So that's -125% fire resist. Any math doctors in the house?

(BTW: has been cake to keep EE fire debuff up reliably by a periodic lightning arrow shots whenever I need to wait for an explosive arrow stack to boom)