Hi and Welcome!!!
Do you have a sump? How long has your tank been set up??
Please describe your system in a bit more detail. IF you have a sump already, or the tank is drilled so you can have a sump. The refugium could be set up first, then you could buy the skimmer down the line.
Kind of a tough question to answer with out all the info on the system. A pic would help a lot as well.. Were you thinking about a HOB (hang on back) skimmer and fuge?? This would make a difference on the responses you get.
Again, welcome to the site and enjoy your stay!!