my .02 - is good on deity; on immortal imho it's already meh. And only on some deity; on an isolated start it's again useless. I mean, on immortal, with experience(I still take it over deity, much more room for various approaches), you should reach what you want without much fuss.
regarding the above question - if at pop. 1 as non imperialistic you work a, dunno, 3 food non farmed corn; your produce towards the settler 3(corn) + 1(base city hammer) = 4/turn.
as imperialistic ideally you want a forested plain hill - at pop. 1, you produce towards the settler 3(hammer) + 1(base city hammer) = 4(hammer) * 1.5(imp.) = 6/turn
without a forested plain hill, at pop. 1 you'd work either a plain forest or a grassland forested hill and you'll produce 2(hammer) + 1(food) + 1(base city hammer) = 3(hammer) * 1.5(imp) + 1(food - no bonus) = 5.5/turn.