I use eSHa test kit - they are strips that you did and wait for 60 seconds and you get 5 test results. They are about £10-12 for 25 strips.
They test for
nitrite
nitrate
pH
gH
kH
For freshwater tanks that only leaves you with ammonia which you can pick up for £3-4
They are well worth the money - 2 tubes will last you a whole year based on testing once a week. Whereas to buy individually you have to pay around £4 per test so thats £24 including ammonia and the strips plus ammonia cost £16.
Also with any medicine or test kits, you should throw them after a year.