What size tank are you planning on getting? what do you plan on stocking it with?
Depending on the above a good quality skimmer will go a long way.
Shop around though, you will find better prices on some websites or even smaller lfs
' will bargain with you.
I have a used one I had on my tank for 18 months or so. It's a hang on saline solutions skimmer. My lfs
sold it for about $100+ but I went to a small store and they ha a knock off one for $50! Make sure you shop around, dont buy anything on impulse!