As for sleeping shelter, consider a few discount outfitter sites that have closeouts on lightweight hiker tents, etc. Sportman's Guide has a British Military issue "mosquito" tent for $18, less than 5 lbs. Hard to beat. On underwear, my #1 choice is cycling short LINERS that are padded with synthetic chamois. Not the full shorts. VERY light, thin, cool and all-day comfort, cheap at Nashbar. Wear one and store the spare in the space of a Red Bull can. Can't say enough about staying away from places like metro Chicago, etc. if you can, use the back roads to double the enjoyment of this trip and see more in less miles, relatively speaking. Your youth will serve you well if well hydrated and nourished along the way. Good Luck!