Well, I started off about 4 years ago with a tank that size, and it was one of the biggest mistakes I made. It is just too small, making it difficult to maintain stable water parameters. This is extreemely important.
Absolute minimum would be a 4 footer. You can get one for around $160 new, so it's not a lot of money (relative to what's to come ;-) ).
Skimmer, you can't buy skimmers in ChCh, none of the shops stock anything useable. Queen, Berlin, and any Red Sea brand skimmers should be avoided at all costs. Auckland might be your only option to buy a real skimmer, unless you want to buy one online and pay sky high shipping. Budget around $600 + for a used skimmer.
Lighting, depends on what you want to keep coral wise. Personally I wouldn't go with anything other than Metal Halide, but if your not interested in keeping coral, then flouro will do. You could comprimise and go with T5's if you only want to keep LPS and soft corals. DIY halides around $500 (dual 250Watt).
"Live" rock, around $12/kg the stuff you buy in shops down here is actually dead (white coral rock). Around $720. This forms an integral part of your filtration system, so loosly speaking, the less rock, the less fish you can keep.
Sand $50
Sump, you really do need a sump. If you get a 4 footer, make sure it is drilled with LARGE overflows. You could uses your 3 footer as a sump. It helps keep unwanted equipment out of the tank, and out of sight.
Test kits - an important part of setting up a tank. You'll need Ammonia, Nitrite, Nitrate, and Alkalinity to start with, then Magnesium and Calcium are necessary once corals are added. Use Salifert kits as these are made specifically for saltwater. Around $30 each.
So thats $2200 absolute MINIMUM before you've got any salt, fish, or corals. You could double that when fully stocked.
Layton