Wolfox

it's hard to say for sure where you should start. best case you read the visual novel for fate/stay night but that's an investment. the anime(s) for fate/zero and unlimited blade works are both pretty good but they'll spoil elements of each other, and zero will especially spoil heavens' feel, so that's difficult. the older fate route adaptation is good supposedly, but not as an introduction to the series. 

tl;dr: there isn't a good answer other than "read the VN first" and that's hardly a good answer lol.