The typical pleasure boat anchor rode is a long length of nylon line shackled to a short length of chain at the anchor end of the rode. The chain is there mostly to add weight to the shank of the anchor, helping the anchor dig into the bottom. The rope part of the rode must be nylon. Nylon rope is not only strong, it is also elastic. When waves roll into an anchored boat, the nylon stretches like long rubber band, preventing the destructive jerking that occurs with a less stretchy rode.
Both three-strand and braided nylon ropes make excellent anchor rodes. Three-strand gives greater elasticity at lower cost, but braided nylon is more flexible, making it a better choice when the rode is fed through a deck pipe for stowage. What size rope do you need? A good rule of thumb is 1/8" of rope diameter for every 9 feet of boat length. In other words, if you have a 26-foot boat, you need 3/8" line, but you should buy 1/2" rope for a 28-footer. To determine how long your anchor rode should be, multiply the deepest water you expect to anchor in by eight. If you expect to anchor in 25' of water, you need 200' of rope.