If, and it's a big if, I'm understanding you, any RAM should work unclocked but supported RAM is more likely to work once he starts overclocking.
Correct. RAM is a fickle thing once you start overclocking, which you won't be doing for the forseeable future so just buy whatever's a good deal (try get a pack of 2x sticks rather than 1x though) and roll with it. If he sticks to it and wants to make it his hobby then start exploring other options.