The dehydrated foods made for camping are generally the tastiest and most weight efficient by far, but if they are too expensive (understandable; they are generally very pricey no matter where you are), there are cheaper alternatives.
There are a wide variety of trail mixes, ranging from the classic GORP ("Good Old Raisins and Peanuts") to much fancier fare. These hold up well in all temperatures, and provide good energy without a lot of weight.
Also consider some staples from the grocery store. In addition to the hardier and more convenient fruits and vegetables (apples last a while, don't require peeling, and aren't terribly heavy; plums, cucumbers and grapes also travel well), there are a number of dehydrated foods available cheaply that make good camp foods. Many fruits are available in dried form, and while high in sugars, they keep exceptionally well, and are very light. Small boxes of dried couscous and rice & bean mixes are great, although they require additional water, and may require small amounts of vegetable oil as well.
For desserts, cookies are light, although they tend to break during hikes. If you don't mind crumbs (they taste the same, after all), they're a good choice for treats. Also the classic S'mores (graham cracker, chocolate bar, and marshmallow melted into a small sandwich over a campfire) is light and fun.
For a treat that will add a little more weight, but may still be well worth it, bring a can of pie filling of the fruit variety of your choice (cherry is my personal favorite, but there are many other options). Over your campfire, pour the fruit filling into a pot, and crumble some graham crackers into the mix. Heat, and spoon yourself some yummy, sticky dessert. IMO it's always good to have at least one can with you, as a can can be a very useful tool for collecting, heating, and drinking water in a pinch.
It is worth noting that many of these ideas rely on having some basic camping cookwear and utensils. If you don't have them, I highly suggest investing in a decent set of light-weight camping cookwear. It adds some weight to your trip, but makes your overall dining options much more flexible, and allows you to abandon some of the heavier food options.