Most people overpack when traveling anywhere. Keep in mind that whatever you need you can buy here-much of it at a much cheaper price, so, instead of buying a nice new jacket for the trip, buy one here. you'll have a souvenir of your visit as well. Things such as t-shirts can be bought for just a couple of dollars. Shoes can be bought in most markets, both dress shoes and sneakers.
Most cosmetics are imported from abroad so are more expensive here, but not by much. As for adventure sports. much of the equipment you will need can be rented here, although, if you want a specific quality or model, you may want to bring your own. In lima you can find just about everything you would find in any major American or European city. also there is so much in the way of handicrafts in Peru, that you will probably want to buy a few pieces. So save some room.
Doing laundry is simple here. Just take your pile of clothes to the laundromat, get your receipt and it will be ready for pick up the next day-all nicely folded. Some places in Cusco and Lima will have it ready within two hours. The price is never more than a few dollars. The lavanderías are everywhere too. Most hotels will do your laundry as well, although not as cheap as the lavanderías. So don't try and pack for your entire trip. Plan on doing laundry at least once, and it will make your packing a lot easier.
For the Jungle, lightweight pants that can zip off the legs to become shorts are good. That way you can be ready to protect yourself from mosquitoes when needed, or cool yourself off. Binoculars, a zoom lens for your camera, a mosquito net if camping, insect repellent, malaria tablets, a wide-brimmed, hat, and sunblock are essential.
In the Andes, the weather can be quite sunny during the day and bitterly cold at night. Daytime temperatures may even require shorts, but at night you'd better be prepared. A warm jacket or sweater is crucial. Keep in mind that wool accessories and clothing are sold everywhere in the highlands, they are quite cheap and good souvenirs. Leggings and thermal underwear are good bets also; they don't take up much space and can be worn under your regular clothes.
For the Coast, one pair of shorts will likely get you by. Only in the summertime isit warm enough so that you will really need them though. Long pants are the norm and at night it can get a bit chilly, so alight jacket or asweater is necessary. If going to Tumbes, follow the same rules as you would in the jungle.