well, mikes on both side of the pond seem to agree a lot.
i'm using api tests currently, but i'm figuring on switching out the phosphate test for a salifert kit, along with picking up a magnesium kit from them. (i've not got one currently, but i need it.)
api is a good inexpensive test that is popular and pretty accurate for most things, but i've read of problems with them reading low end phosphate and i'm not even sure they make a magnesium test. you'll hear people swear by this kit or that one, but as you read around you'll get to know which ones are generally accepted as accurate.
a refractometer is going to be a VITAL piece of equipment for you. look for one with automatic temperature compensation, ATC for short. i use this one:
http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+4690+9957&pcatid=9957 . it will be important, no matter which one you choose, to make sure it's calibrated properly. most of the available devices are actually not designed for seawater, but that's easily fixable by calibrating with this solution:
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=18717linked in the previous article i posted, written by one of the resident chemistry gurus around here, randy holmes-farley, is this:
http://reefkeeping.com/issues/2006-12/rhf/index.php . it's a pretty comprehensive explanation of what to look for in a refractometer, how they work, how they don't, and how to calibrate them. give it a read.
i'll again back up what mike told you and say that in the beginning the 'extra' test kits aren't really going to come into play. the basic parameters you'll be concerned with are ammonia, nitrite, and nitrate. these are the levels by which you'll be able to monitor your initial nitrogen cycle. once that's complete, i.e. ammonia and nitrite equaling zero, and nitrate being reduced by your first waterchanges, you'll be ready to add your first livestock. GO. SLOW.
you're creating a living ecosystem here from scratch, and it takes TIME. patience is probably the best thing to learn first off. take the time that you'd otherwise be pulling your hair out and itching to get your hands in the tank and add all kinds of fish and coral and what not to READ A LOT. think about what fish will be able to live out their entire lives in the size tank you have and which ones they can or can't live with. think about what kind of corals you're interested in, and read everything you can get your eyes on about their care requirements, allelopathy, aggressiveness, etc. keep asking questions, and most of all be patient. there's a lot for everyone to learn with this deal, and many folks will be able to share their experience and help you, and me, along the way.