For starters the API test kit should be just fine. You will need the kit though for your cycle so you might wanna pick it up sooner than later/
In the future, after you get a bunch of corals you will most likely want to invest in the following kits: calcium, alkalinity, magnesium and phosphates. I personally do not like the API versions of the above tests, not accurate enough and hard to test, I went with salifert kits, a bit more money but definitely worth it in my opinion.
Good luck and post away when you need to!