On my touring bike, I have a White Industries 46/30T crankset, which gives me the option of going lower if I need to. On the back, I have an 11-speed XT long cage derailleur that easily handles a 42T cassette. Having said that, the 36T in the back and the 30T in the front give me as low a gear as you can find on commercial touring bikes. I use Microshift bar end shifters -- friction for the front/left, and the mountain-compatible version on the back/right. [Microshift now also makes its own 10-speed (Advent X) derailleur, cassettes, etc. FWIW. My kid is using it now having tired of 12-speed.]