Here is where rendezvousing comes in handy with writing. 

 Note: We don't do traveling like this, I just learned this stuff by being at/in rendezvous. 
A traveler from a fantasy/medieval/pioneer era would want to take only the barest necessities since they're going to have to carry it the whole trip. I'm not sure if you guys have ever been on long hikes with backpacks or not, but it can put a lot of strain on your back and especially on your shoulders. *knows from experience*
Bedding: The norm would be a wool blanket because even when wet it keeps you warm. If needed to, you can also make a poncho and/or cloak from it. (Unless they're already wearing a cloak...which should be wool as well.) Wool comes in various thicknesses, so a thick wool would be great for bedding and medium/light weight wool would nice for capes & cloaks.
Food: If they are journeying they'll want to pack non-perishable or long lasting food such as dried meat/jerky, dried fruit, and nuts. Herbs are great because they're medicinal and add a lot to a plain dish like potatoes. ^^
A canteen of water is good too. If they come run out of water and refill their canteen, be sure its a clear water spring otherwise the bacteria in the water will give you....ickies. *also knows from experience* Never drink water from a creek down stream of a cow pasture.  

 If the water is cloudy make sure they filter it through something before adding bleach (if bleach exists in your story.) If not filter it through, say cheese cloth, to get and debris out of it and bring it to a rolling boil for one minute. Cool before drinking for obvious reasons. 

Travel clothing: If your character starts out on their journey they are wearing one set of clothes, yes? Then they can pack one more set of clothes in their pack just in case their present clothing gets soaked or soiled for some reason. Then they can always wash the clothing in a stream and let it sun dry. Starting out, I think for a guy, a shirt/tunic, leggings/pants, good leather boots, a cloak/cape with hood, and gloves/mittens would suffice. For a girl, a chemise/shift, skirt/dress, tunic (if wearing a skirt), leather boots, and gloves/mittens. 
Both may want 2 spare shirts (or chemises for girls). A thicker one for cooler days and a light cotton one for warm to hot days. Gloves are handy for cold weather, or depending on what they are made of, taking hold of sharp things such as thorny briars, glass, or a sword (for uncallused hands.) 
 
 Some other items to put in the pack would be a knife or hatchet for cutting firewood or kindling or using it as a defensive weapon, rope, a tarp probably made of canvas that has been oiled or has a thin coating of beeswax to prevent rain from soaking through, four iron stakes, a large cup, spoon, and flint and steel to start fires. The rope, tarp, and stakes are great for making a quicky tent if bad weather approaches. (My dad and I made one between two trees last summer.) Also, people can eat anything from a cup because it holds solids and liquids. Spoons too! (The knife can also be for cutting meat, for example.) Then you only have 3 eating items and less dishes.  
 
 I hope I didn't give you an information overload. >< I only desire to be helpful. ^^
Good luck!
~Calen