Which tests would you most like to see? I have an order getting ready to ship to me in the next couple days that I need to replace some things on. Here's what I can get and what I can sell it for. I don't have access to many of the refill packs yet.
magnesium refill (3 pack) $18.95
calcium refill (3 pack) $7.95
I would purchase the Nitrate one since I need it.
You should probably get the generic ones: nitrate, nitrite, ph, kh, gh, ammonia...maybe even the phosphate or copper (for the shrimpers).