i wouldnt buy a R32 GTR fuel pump.. buy a bosch 040, or 044... what point is there of replacing a 10yr old pump, with a 15yr old pump? they are about ready to die anyway
boost gauge - there is a nipple on the back of the plenum with a rubber plug on it, in the R33 it goes to the factory boost gauge in the dash, in the stagea its blocked off, just put your hose on there, done!
pod filter - apexi power intake is a great filter, i had one on my 33, and kylie has one on her stag.
BOV - get a turbosmart plumb-back bov, the stock one can leak over about 12ish psi
FMIC - the stagea specific kit is identical to the R33/34 kit.. which i installed in kylies car, definately worth it if you want to raise the boost (the stock side mounts are VERY restrictive, kylies stag spooled quicker with the FMIC)
Exhaust - 3" turbo back with a split dump (dont get a bellmouth dump, they are useless, and cost about the same) with a 3" highflow cat.
if you want a bit more top end power, but are willing to drop a bit of midrange, get a 3.5" system. (my R33 made 300rwhp on stock turbo with an exhaust that started at 3", and gradually expanded to 4" by the end)
Auto shift kit - MV automatics in SA, have never heard a bad word about them
Boost controller - $30 ebay special! i'm serious, i had one on my R33, boost never spiked over the 13psi i set it at.
if you have bigger plans, or want more control over wastegate opening, etc.. get a electronic boost controller, but for a mild upgrade, they arent worth it.
you will probably want to get some form of fuel management too, SAFC II is fantastic for mild power.