Dotchess,
#14 wire will be adequate for your LED lights. Fuse them for 5A and you will be fine. I don't know what your spotlight draws, but since they plug into a lighter plug and those are usually rated for 10A, I'll use that number. I'm going to guess that you will have a short wire run to the lighter plug, so you will probably be fine with #12 wire for that one. I would fue it for 10A, since that is what the plugs are rated for.
Since you are using a fuse box, it should be located as close to the battery as possible. The more wire between the battery and the fuse, the more wire that is left unprotected. Put every DC device on it's own dedicated fuse. here's a link to West Marine's chart for determining wire sizes for various applications. It states this, but I will also, use AWG wire, not SAE. SAE wire is smaller and carries less current for a given size. Also, be sure to figure it on the complete wire length, pos and neg, because current goes to the device, but also has to flow back to the battery.
https://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&catalogId=10001&page=Marine-Wire