If you are going to do a fowlr
tank then all you need is some live rock and aragonite substrate. I would suggest buying around 20 lbs of live rock which you can get from bulk reef supply for $3 / lb. If you want to go with a reef tank however you will need to upgrade the lighting system which is expensive.
It is also HIGHLY recommended to get a ro
unit or secure some way of acquiring ro
water from a lfs
or fellow reefer in your area.
Some other things to look at is adding a refugium onto the tank as well as a skimmer.