We've tried two different water-to-coffee ratios:
2:1 - this concentration is good for mixing with milk or water. I actually used the same grounds four times before discarding them.Neither really stands out as a favorite, but 4:1 is less work.
4:1 - close to the usual french press ratio
I've also been enjoying a lot of cold yerba mate, which like coffee brews in cold water just fine. A french press works great for mate, as does the ol' jar + bombilla method.