Please do not even invest in buying the strips as they are inaccurate most of the time. The go stale very quickly every time you open the container which causes even more inaccuracy.
Liquid test kits are the way to go. I have an API Master test kit that includes testers for Ammonia, Nitrite, Nitrate, pH and High range pH. All of which are the basic testers you need, especially the Ammonia, Nitrite and Nitrate.
I got mine for around 35 US Dollars. If you buy each liquid test kit individually, they are more expensive this way.
When the tank is cycling fishless, test every 2-3 days. If you unfortunately have to cycle with fish (not recommended), you have to test every day along with water changes. After a cycle is complete, you should test at least once a week for Nitrates and pH. I personally test for everything once a month and the day after a water change.