Since I do reef tanks and I already have a pH monitor, I buy the top three - Calcium, Alkalinity and Magnesium. Since a hanna phosphate checker is more accurate than any titration test kit, that's what I use for phosphates. I have a pretty good eye for when the tank is going good and when it is going bad, and so after the initial cycle, I never use an ammonia or nitrite test kit... and typically don't even test ammonia and nitrite when I cycle a tank anymore.
It's basically up to you and what you are looking for. I suggest a kits that comes with nitrate, phosphate, calcium, alkalinity and magnesium, especially after your initial cycle.
Good luck and I wish you the best. I hope you share some more pics of your tank in the future.