Ok, so just generally speaking...
Trolling motor can be hooked up directly to your battery, or go thru a plug & receptacle. Either way I'd put a circuit breaker on the + side close to the battery. Since it's probably a very short run, if you have to add wiring I'd use whatever gauge is on the TM, which is probably 10AWG. Using 6 or 8 AWG would be better. So, positive side would be battery > breaker > (receptacle + plug if you use one) > TM, and negative would be battery > (receptacle + plug) >TM.
The cleanest way to run everything else is thru a fuse panel for the + side, and a ground busbar for the negative side. The advantage to a fuse panel and busbar is that it keeps all your wires and fuses organized and easily accessible. So for the positive side the run would be battery > breaker > fuse panel > switch > accessory pos. Negative would be battery > ground busbar > accessory neg. The exception would be your stereo, which doesn't need to run thru a switch because it has one built in.
Switches for the livewell and bilge can just be simple SPST on/off switches (altho you can get fancier).
For the navs I'd suggest a a DPDT on/off/on switch, and wire it like this:
You could also buy a combined fuse + switch panel.
Fuse size is dependent on the accessory.
Breaker size is dependent on the total amp load of all the accessories.
Use tinned marine wire. Wire size is dependent on the amp draw of the accessory and length of run in both directions (pos and neg). On a 14' boat, with a short run from a stern fuse panel to switches near the back bench, I'd guess that 14AWG would be fine, 12AWG would be better. Again, the exception might be the stereo which may draw more amps.
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Hope this helped.
RR