With a couple dozen bamboo rods of all manner of makes, lengths, tapers and conditions in my quiver, I can tell you it's a very personal choice, so experiment. Bamboo is an extremely strong and resilient material (they build scaffolds out of it to construct skyscrapers in the Orient), so don't fear breaking it with a particular line choice. In fact, I've found bamboo rods to be quite tolerant of a range of line weights and types. My personal favorites are the Wulff TT lines and Cortland Peach lines, though many other makes and weights will work as well.