I have been doing for 3 years
What have you done in those three years?
(Just a question, not being mean!)
I really want a reef tank too, my LFS suggested freshwater first.......
12years ago.
I've probably spent an equivalent of $500 on books associated with marine tanks. Still no marine tank. (Well, I have it but it's full of freshwater fish)
If you're confident you know your water, crack on..... But it's a big mistake if it goes wrong! Most marine fish are 5-10 times the cost of a freshwater equivalent.
Basic shoaling fish tetra £1, green chromis £5-6
Salt bucket £50-60 (biggest size) depends but 2-3 times a year on this.
Refractometer £20+
Skimmer ------£100-£500 (for the tank size)
Live rock. £6-10 per kilo
Sand.......
RO water (maybe you have one? £50-£150) or purchase water? Probably not cost effective.
Water containers.........
Test kits.
That's your budget gone.........
Not sure what fish cost wherever you live but £30-£80 is not obscene for a marine fish.