My beloved 2001 Litespeed Tuscany and my 2014 Cannondale SuperSix EVO Hi-Mod Team bike
If by "hill" you mean something that requires effort, then a 3 speed will not work. You'll end up walking to the top. Hills require gears. Any reason you don't want a bike with many gears?
When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking. — Arthur Conan Doyle
back in the day (as in my early teen years, where I had nearly an infinite amount of energy......ahhh how I miss those days), even a 10 speed was pushn it on hills! IMO, I won't go with anything less than 21.