... I'd shoot for something like this:
If you're really worried about drivetrain efficiency (in this case, I wouldn't), use the largest chainwheel and cog you can...
I'd have to agree with both points.
When it comes to gearing choice for a three speed you're better off gearing your top gear for the flats, that way you have 2 lower speeds to choose from for climbing hills depending on their grade, IMHO a better option because you really don't need gears to get down a hill. What works for me is something close to the following ranges:
3 - 76 g.i. - flatland travel
2 - 57 g.i. - moderate hills or strong headwinds
1 - 43 g.i. - steep hills, snowy/slushy streets
My Brompton's stock gearing (50/13) was approx. 82-62-46 gear inches... 82 was a little too high for the flats unless the conditions were perfect and I was feeling fresh (and wasn't lugging around over 20 lbs of gear) and 62 was a little too low but was decent in headwinds. If I chose 2nd gear to be my main (flat) with what I feel to be the most comfortable then the gearing would end up being 100-75-56 using a crazy 56/12 chainring/cog combo... that's nuts.