Do the math and let your legs be the guide. I have two examples of 24-inchers in my garage that get significant ride time. One of my favorites is a Huffy Good Vibrations that is set up 40:18 (40-tooth chain ring and 18-tooth freewheel cog) for a ratio of 2.22. It has 6.5-inch cranks. I mention the cranks because, while they don't change the ratio, they definitely change the ergonomics and feel of pedaling. My wife's favorite is a Dyno Glide 24 with 44:22 (2.00 ratio) and 5.5-inch cranks.
Mess around with different gear ratios and cranks and your legs will tell you what's good. Of course, it also depends on what kind of hills are in the neighborhood. Also remember that 24-inch wheels and 26-inch wheels will be different (bigger wheel will be harder to push at the same gear ratio). Have fun!