What are you hunting for? Idaho varies widely in terrain from high desert in the south, wide open mountains in the middle and super dense forest in the north. What you bring depends largely on the area you'll be in.
Every thing light weight including the gun and I used a badlands 2200 pack every thing light weight in the pack water purifier and freeze dried foods and the little water boiler for the food lots of jerky and electrolytes powder for your water get into shape its rough countryCamping by the truck or spiking out?
Get a good compass and an accurate map and learn how to use both. GPS is nice but electronics do fail and the odds of a compass not working are slim to none. Idaho is rough good boot would rate high on the list along with a membership to the gym good luckI haven't decided yet which one leaning towards backpacking or spiking out.
You had better start right now getting in shape it takes a long time to get into the shape necessary to face those mountains. Are you meeting somebody out there or are you going out blind on your own? This makes a world of difference and hopefully you'll have somebody out there with a quipment already available. If you're going out blind, then I strongly suggest you contact some out outfitter or m.p guide or you may be facing disaster. It's awfully easy to get lost in those mountains.The most important thing is be in shape. Other things will then be fun.