Okay one thing you have to remember is....even if the test kits cost 30-50 bucks they usually last a few months....
For FO, or FOWLF API has a test kit that tests for high range pH, ammonia, nitrite and nitrate its like 20.00 at petsmart...If your going with a reef then you'll need that kit and the reef mast kit that tests calcium, carbonate hardness, phosphate and nitrate levels for about 30.00
So both of those together its 50.00 and they last a while!
Hope this helps!