you can hunt around for bargains, good equiptment is still worth buying second hand but dont expect it to be dirt cheap because its got a few miles on it.
there are four main areas of expense
skimmer
good skimmer, dpends on wether you want a sump as to what type you can get, the deltecs are the best hangon back type skimmers. if you have a sump it allows for more skimmer choices
Lighting
depends on what corals you want to keep
flow
the more the better (generally)
stock
rock is the biggest expense, you can find second hand live rock or the occasional bargain on trademe (all the better)
then your nice fish and corals