How is it that you can create a settler first, and then get him out there to grab early copper or horses? If you're crafting a settler first, you *definitely* do not have BW (so don't know where the copper is) and as often as not do not have AH (so don't know where the horses are).
This is not something calculated or studies so there maybe holes in it. Imperialistic and capital on +3H hill I can think of. But usually with common capital +2H+2F+1C and a worker on +2F+1H (Grass Forest, should be quite common) tiles it should take 38 turn. Hunting and Mining are both little over or less 10 turn and BW and AH are 20. So that's less than 38 turn but you can't have both of them but if you start with hunting or mining and wait 10 turn after your settler you are pretty close to get them both, but if you don't want to wait, what I like to do in this case is a build a city and research archery for barbs and still it's good solid start the best in my opinion if you aren't going for early wonders.