light or medium gauge, D'Addario phosphor bronze. so the EJ 16 or 17, depending. give the 80/20s a try too as they are brighter but mellow up in a week or so and age well. but PBs are warmer.I just got a 76 D25M spruce top mahogany and would like to know what are the best strings and gauge to use? I like a warm deep tone. Not to crisp but very deep bass sounding. Any help?? Thanks.