Well, to start with the basics:
Live Sand - Depending on where you get it will depend on how much it will cost. Go with live though so you don't have to wait for dead or southdown to seed. You should shoot for about
Live Rock - Very important. Go for about 1-2 lbs per gallon. That would mean between 29 and 58lbs for a smaller tank like the one you're planning. Avergage price of LR
is $5/lb so you're looking at about $145- $290 for LR
. Don't skimp on the LR
though, its the best natural filtration and you won't be sorry. If you're on a budget, you can put down base rock which is considerably cheaper and seed the tank with a few good pieces of LR
. That will get the bacteria growing on the rock and should cause the coraline to grow (will take time though).
You'll only need a heater if where you are is colder. I live in Florida and a heater isn't an issue. I have a chiller to keep my temp between 78 and 80. You'll have to make that call based on where you are and what the temp range is.
You'll need lights. What do you plan on keeping in your tank. If you're planning a reef, shoot for between 4 - 5 watts per gallon at minimum. Some have more (FWIW, I run 5.12 watts most of the time and then up to 8+ when the MH
is on). This will be one of the largest expenditures you'll make. Look for used stuff or go eBay to save money. You can even build stuff yourself, which is a great way to go.
Filtration - Ultimately, if you have enough live rock and a healthy sand bed, you shouldn't need mechanical filtration. You should consider adding a sump or refugium which will make for a healthier tank by increasing the water volume of your tank, increasing filtration (via nutrient export) and by providing a source of food for some inverts and fish). A good skimmer (over sized for your tank) is always a good idea. Just starting out, you should have one.
I could go on and on... but I think you get the general idea here about the basics.
It sounds like you're just starting out. The best advice I can give you is READ, READ, READ and be patient. This hobby can't be rushed. The more you know, the healthier and happier your tank's inhabitants will be and the better your tank will look.