Plenty of good suggestions already but I for the under cabinet kitchen lighting (16' strip of cob LED) I installed a few years ago I just used thermostat (18/2 I think?) wire to run the gap between cabinets.
Just don't make the same mistake I did and use the cheap solder that comes with the kits, it was such a frustrating experience until I bit the bullet and bought some nicer stuff, made the process WAY easier