It's not really about WHAT you need...it's about how BIG you need it.
As a start, once you decide what size pond/tank you want to keep, double the skimmer. So, if you're keeping a 400gal. tank, look into skimmers that are rated for 800gal. tanks.
Refugiums, IMO, help greatly and are almost a must. The bigger the better.
It's mainly about doing common and routine maintenance....water changes, filter changes, etc.