First...Do Research.
Figure out what you have had luck with in the past if you have been in freshwater.
Find an LFS local to you that you think you can trust, then double check what they say here on the BBS.
Then and only then buy your equipment, fish corals etc. There are many methods for setting up a new tank. Everyone here will have different opinions. I would recommend to first get the book "Conscientous Marine Aquarist" by Robert Fenner. It covers many different aspects of the hobby. The reason I say this is because what I use is not necessarily what someone else will use. Many people will say just get a 4" DSB, a lot of live rock (100+ lbs in a 90 gallon), a skimmer and some power heads. I would hold off on the skimmer until after your tank has been established or not add one at all. In a reef tank I would wrather see people setup a refugium for ultimate tank health. This will provide beneficial filtration and life for your system. Most LFS's are going to try and sell you Wet/Dry filters which are not good in my opinion, but they will work.
I personally use Undergravel and people think I am nuts, but it has worked for me , I am used to it and I know it works for long periods of time with routine maintenance. The key is to do research, before making purchases and by coming to this board before purchasing anything you have definitely taken the right step.
If you want to go with modern recommendations here is what I would suggest.
90 gallon tank and have it pre-drilled for the overflow.
VHO or Metal Halide Lights ($300 - $700)
DSB (I use Carib Sea Reaflor, others use Southdown sand)
Live Rock, make sure you check here for places where people get their live rock from. This site supposedly sells some great live rock, but I personally have never used it.
Powerheads (2 Hagen 402's or compatible, 1 Hagen 302). This will provide more than enough circulation in your tank.
Build a refugium that will connect to the over flow and get a pump that will give you sufficient return.
The overflow should go into either a refugium or sump. In the sump you can put your protein skimmer at a later time. You can also put things like your heater to help remove them from the tank.
With this setup you should be good to go. Most of all realize this hobby is not cheap and that shopping around is a must. I hope this long winded answer helps give you some different ideas to consider and to take into a LFS before purchasing your equipment.
--Andy
