The two best bang for the buck are NO2 and new gears for the rear axle.
system can be tuned to the horse power gain you want, but you should stay below 250hp shot. Nitrous has the advantage of being switched on or off as needed. $500-$800
The gears will give you snapper performance all the time but will hurt fuel use. $180
Using nitrous can break parts(engines, transmissions, u-joins etc.) Gears will not but will make it easier to shred tires.
You may also look into installing a locker with both these options. One tire burnouts are for squids.
Reprogramming the ECU only gives a gain of 20 -50 hp, this would only reduce your quarter mile time by a tenth or tenth and a half seconds. the right gears or nitrous will cut 2 seconds off the quarter mile.