What I would do is buy it all separate. U need 10 lbs of sand. A heater, thermometer, if u way it to be a fowlr
then about 8 ish lbs of dry or live rock. Some type of filter.( if you are going with a filter I would go with one rated for 30gal. It will move enough water so you don't have to have a power head. And a light system. For the lights you can get a small hood for the tank. I recommend a t5 ho
florescent bulb. A hydrometer or refractometer. And salt. That's about all you need beside the test kit. Depending on prices you are looking around 100 - $200 for the initial set up. I would not recommend a starter kit.