Does your boat have a windlass?...
If so that will determine the chain link size. If not, 5/16th inch is a common size. Several galvanized grades to choose from; proof coil is the lowest grade followed by BBB, high test, grade 70. Our boat came with 50 feet of high test with 250 feet of 5/8th inch three strand nylon rode. Of course our boat displaces 30,000 pounds. If you boat comes in at around 8,000 pounds perhaps 7/16th inch three strand should work. I would stay with 50 feet of 5/16th inch chain to help with catenary. Of course this all assumes that your cruising anchorages are mostly mud and/or sand. If not then you need to rethink your anchoring system.Terry