If I were you, I'd be focusing on lightweight items that can't be improvised or easily replaced. A lot of people end up with either heavy, bulky survival kits...or ones that are useless. The trick is to know what you need, and what you can do without.
The second concern is budget. Not knowing what your price range is, I can't really get too specific. And generalities are fairly useless. But I'll make an effort here anyway.
The basic essentials are water, food and shelter. It can be assumed that someone who is going camping probably owns a canteen and tent, or has access to a water tap, or is staying in an RV or cabin, or whatever, depending on the camp ground. Food, likewise, is rarely an issue when deliberately going camping; Even shelf-stable food must be rotated and replaced sooner or later, so it's best to focus on water and shelter.
For shelter, I'd put in at least one mylar "space blanket" for emergencies, a sturdy but compact tarp, a bundle of at least 100 feet of strong twine (paracord 550 works nicely) and a compact rain poncho. You may be able to find a tarp that has a shiny side, like a space blanket, to serve double duty.
Emergency water supplies can get expensive FAST. Even a dirt cheap (read: not very effective) water filter or purifier can set you back $40-$50. A decent but economical one can be $100-$150. MSR's MiOX purifier is very compact, and works very well, but is also very un-cheap. First Need is another good brand. If your friend camps near salt water, you might want to also include a solar still; I've seen cheap ones that are folding/inflatable. Of course, if cost is no object, I've seen a water filter than can desalinate water for $1200.
Next, one of the essentials, whether you're a stone age reenact-er or a high-tech ultralight backpacker, is fire. You don't score any points, in an emergency, by being virtuous (whether by choice or necessity) and foregoing a fire. In an emergency, heat can be life. So, a good fire starter is a minimum. There's many options, but probably the best one is a combination. For actually lighting the fire, go for a product called FireSteel. It's a high-tech version of flint & steel. Combine that with an accelerant of some sort (petroleum cubes, simple tinder, or a magnesium firestarter) in a waterproof container, and you'll be set. If your budget is large, a compact camping stove and a fuel canister or two (MSR makes some very good ones, such as their Pocket Rocket model) might also be a good idea. Matches and a waterproof case are the cheapest, but also the least effective option.
Communications comes next. No, I don't mean a cellphone. Basics include a mirror (the space blanket from above can also do this in an emergency), a BRIGHT flashlight, and a very loud signal whistle. A spare battery for a cellphone might not hurt either.
Then, we have tools. While any fool can pick up a rock and have a field-expedient hammer, some tools are not possible to improvise. A good knife is essential. If you get a multitool (Swiss army knife, Leatherman, etc) you also get things like screwdrivers and can openers along the way. Nothing sucks worse than finding out all your camping food comes in cans, and nobody brought a can-opener. Some means of cutting wood for a fire is also necessary, but hatchets are bulky. A better option would be a wire saw of some sort; They're cheap, easy to use, effective, and difficult to accidentally cut yourself on. A miniature sewing kit is another example of a tool or set of tools that is difficult to improvise. A compass is another essential tool, when away from civilization.
At least a small first aid kit should be included. Ideally, one equipped to handle broken legs or arms (wire splint, stretch bandages, etc).
Lastly, we have the case for the kit itself. It should be sturdy and comfortable to wear. Camelbak makes a number of small packs, including belt packs, that incorporate canteens, which adds some additional usefulness to the pack itself.