The basic rule of thumb is to pull 2* of timing for every 50hp increase in nitrous. So if you run a 50 hp shot and your timing is usually at 13* drop it back to 11*. If you feel that you can increase it then go ahead.
Up to a 100 shot I ran the stock heat range plugs gapped at .035" up to a 100 shot. After that I dropped down a heat range for each 50 hp increase.
I also would recommend the following other pieces, most of which has already been said but you really need them to keep it safe. A window switch, I have mine at 3k on and 6k off. It has saved my ass on missed shifts. WOT switch, you don't want to spray nitrous, especially a wet kit, at other throttle positions than WOT since you can get puddling in the upper and that is not a good scene. I would also upgrade the fuel pump, you'll probably be ok with a 100 shot but anymore and you will definitely need an upgrade, I run a 255 LPH pump. If you want to run it at the track, depending on how strict they, you will also need a blowdown tube. I didn't see one in the pic but I also might have missed it.
Run the stock fuel pressure since it is a wet kit.
If you are at the track and make a nitrous pass and want to check the plugs get on the return road and shut the car down and check them as soon as you get off the track. The drive back to the pits can hide the signs of detonation. Look for silver flecks on the sparkplug porcelain and any other damage to the plug, broken electrode and such.
Other than that start small and get comfortable with everything before moving up in power. And it is extremely addictive so have fun.