Help choose a better upgrade for my MacBook5,2
Snow Leopard, Lion or Mountain Lion. As da4 mentioned, you will need to find out the capabilities of your machine and look up the requirements of the operating systems I listed.
You could do what I did to my macbook which is install a solid state drive and 4gb of ram and get mac os sierra patch tool and download mac os sierra it runs great on my computer with no issues it was definitely worth it.