To save money on road trips, I often camp along the way. Sometimes I don't camp every night, but every other night. This all depends on your trip. Anyway, it is also a good way to experience the local flora and fauna (especially bugs) in a real intimate way. There are some things so that you will have a minimum of comfort during your one night stay in the outdoors. I have learned all of this through trial and error.

A tent that you can easily carry and roll up I am on my second tent, since while sleeping in my first tent, my feet touched the walls and sprung leaks in the rain. I bought the new one while out on the road at Wal-mart. You need a tent that leaves about a foot clearance on each side. If you are alone, a small one will do as you can adjust your angle inside. I am using an 8x8 now and am very happy. It is easy and quick to set up (at least when the sun is still out) and has zipper-able windows and a roof for ventilation and to protect from the elements. I also have a few pouches to store my keys and glasses and a door to store my shoes. I love my tent. It has saved me a lot of cash and it is better than sleeping in the car. (Sleeping in the car is not good for your back or your sanity.) Bring a small battery-powered lamp for light.
Air Mattress and a decent, small pump Do not get a pump that craps out on you like I did and was forced to blow my air mattress using lung power in The Middle of Nowhere, Wyoming. It really ruins a night. I used to sleep on pads, but moisture from the ground and the hardness make it tough for a wuss like me to get shuteye needed for the road. So now I use an air mattress. It is nothing fancy at all, but it keeps me off the ground. Blow it up so that it is firm and throw it as quick as you can into that tent before the bugs find out the flap is unzipped.
Tarp A good vinyl tarp can act as a roof or as a basement. You should know that the ground sweats during the night and if you do not have a tarp beneath your camp floor, you will get some of that water in your tent. I have woken up many nights with drenched socks and cold feet. Wipe it off with a towel and spray it with disinfectant with each use.
New stakes and a mallet For each trip you should get new stakes for the tent. I like the ones with the green tips which aid in hooking and setting things up. They should be thick and strong and long enough to find solid ground if it is wet out.
Sleeping bag and a pillow Bring a sleeping bag no matter how warm you feel it will be. At night it gets cold, especially out west. I made the mistake of thinking I was saving space on a trip and left mine at home in lieu of a blanket only to end up shivering the whole night. It is best to sleep in the cold with a knit hat on your head and socks on your feet. Do not wear too much beside sweats while sleeping. Your body will produce the heat needed to keep you warm. You only need to trap it.
Lint and matches Collect lint from your drier, toilet paper, or use papers collected along the way during your trip to start a fire. Many campgrounds require you to buy wood on site so don't lug it around. A fire provides entertainment, s'mores, and mosquito repellant throughout the night. Make sure your tent and car are not too close to the flames.
Water and food If you are in a wild location and plan on cooking, try to do it away from your sleeping area like in a picnic grove a few blocks away. Keep your food in the trunk. There are critters and beasts that come to campgrounds at night looking in your car windows. I found footprints one night of a raccoon all over my car. He must have been trying to get in for hours. Water should be brought in the tent in case you need it during the night. You will hear coyotes, deer, frogs, crickets, flies, and other odd and end creatures all night long.
Flashlight Carry a flashlight with you in the tent and outside. It will help you spot dangers and help you know where you are going.
A knife Good for cooking, cutting, and stabbing intruders. Remember that most campgrounds have little in the way of security. I have also used a baseball bat to make me feel safe while cooking not too far from a bear in Ontario.
Things not to bring into a tent... Television, snack food, shampoo (keep it in the car if you must), perfume, jackets, wide-brimmed hats and baseball caps (a knit hat will do)... KEEP IT SIMPLE so you can get moving in the morning. The goal is speed. See my camping page...