No additional fuse needed. The taps are protected by the fuse below them. BATT = HRN/DME, IGN = IGN/GAGS, ACCY = RADIO, LPS = INST LPS, CLOCK = TAIL, PWR = PWR (breaker), and WDOWS = WDOWS (breaker).
Wire size is selected as a function of fuse capacity. The fuse protects the wire, not the load. A gauge only draws a couple hundred miliamps. But the IGN/GAGS fuse is 15 amps. So you should have a wire that if it shorts to ground can safely carry 15 amps to blow the fuse without damaging the wire. Personally, I use mostly 16ga for under-dash wiring, gauges, alarm systems, etc. 16ga is safe for up to 15A fuses, and will be Ok with 20A fuse if the run isn't more than a few feet. 14ga is better with a 20A fuse.