after being off my FG bike for about a year i resurrected my beater with a 50:21 ratio which comes out to about 67 inches with 32's. its comfy for quick little blasts but downhills are too spinny for me

on my geared bike i find myself mostly in 42:15 combo which is around 75 inches and the same size tire and seems perfect for flat ground and i dont find it hard on the hills on my commute

depending on what bcd your crank is, a chainring isnt always more expensive than a cog. surly makes nice cheap rings in a variety of sizes, or amazon has lots of sugino rings that are dirt cheap too

just some food for thought

ps: this little applet is a great calc for skid patches gain ratios inches rpms and anything else youd wanna know