There are tons of Car Camping lists and how-to's out there. Some of those are very helpful, others are just another way of creating advertisements. The list below is not going to be revolutionary or groundbreaking by any means, but hopefully a useful list of what I find necessary on our overnight trips (and no, none of this is in any way an advertisement).
When I first started drafting this post, I thought this would be a quick-and-dirty basics list. As it turns out, there's a whole lot of individual items that I find make a car camping trip really enjoyable. I've separated a section of items not necessary but nice to have, as well. I try not to nerd out on the fanciest of gear but do like to buy things that work and are of good quality. Add, subtract, or multiply as needed, but the following should get you through an overnighter and still let you feel like you've roughed it a bit.
Try to keep this in mind when assembling your kit: You'll always notice the bad in any particular item, but in general, you shouldn't ever notice the good. The point is, your gear should work so well that you don't notice it. Comfortable/dependable/quiet/durable or whatever descriptor it needs to be, it should be. That being said, if you're just an average dude like me, buy the best you reasonably can. Shop the outlets, the seasonal sales, the past season deals, or whatever. Just don't buy economy brands for the important stuff.
Now, onto the list:
3 Season Tent - Your tent is (or should be) the biggest investment in your car camping kit. The Ozark Trail tent at Walmart ain't gonna cut it. A busted zipper, poor water-resistance, material that flaps in the wind, etc. are easy things to point out in a cheap tent. The less tangible, but more important characteristics are things like: Does it condensate too much and does it breathe well? How well does it pack down/how big or heavy is it when packaged? How flimsy/reliable are the poles or the tent and fly material? Mass market brands are great at making things convenient and cheap. Yes, it might be the easiest tent to set up and tear down ever, but will it allow you to be comfortable at night? That's what makes a good tent.
For the last few years, I've been using an REI Half Dome two-person tent. It's been reliable, waterproof, and doesn't seem to condensate too bad (but could be better). Catch REI's many seasonal sales events and you can pick up one of their newer models on a great deal. If you're just starting, these tents will serve you quite well. Tent size is subjective, everybody has their own situations to account for. I bought the two-person because it was just big enough for me to use to change in at race weekends but it also worked well when I had company tag along for an adventure (fits a twin-size air mattress).
I've recently upgraded to a 4-person tent because we needed something larger for our little one to tag along in. I found a good deal on an Alps Mountaineering tent at Backcountry.com and decided to give it a try. Aluminum poles and polyester/polyester taffeta body and fly were good enough features for me to pull the trigger on.
You'll likely have sticker shock when you look at a $40 Ozark Trail compared to a $400 MSR tent, but comfort and reliability are things you shouldn't cheap out on. Shop the sales and you'll likely find a brand with the same quality at a steeply discounted price.
Be realistic about your sleeping equipment. What time of the year will you likely be camping? Do you actually need a sleeping bag or will a heavy blanket be more than enough (and probably more comfortable)?
I have a zero degree mummy sleeping bag that I've used in 20 degree temps. It worked, but temperatures aside, it is not comfortable to sleep in. I'm a side or belly sleeper so laying flat on my back just don't work for me. How often have a needed a down sleeping bag for camping? Probably 8-10 times in the last 4-5 years. It works when it's necessary but is it necessary for you?
I also have a 40 degree, cheap Coleman sleeping bag that zips out flat. I bought it at Walmart several years ago and it's gone with me on most of my car camping trips. It works fine, especially when overnight temps in summer hover around 70 and humid here in Appalachia.
Also worth a mention is the fact that a degree rating is not at all reliable. For actual tested and rated brands, a degree rating means you won't die when temps flirt with that temperature but you will not be at all comfortable. Mass-market-brand temp ratings are basically pulled out of a marketing book and have zero scientific basis for those claims.
We've also taken blankets used around the house. A woven blanket is breathable but still warm enough for a tent in the summer. We've gone this route just as much as others and have nothing to complain about.
Sleeping Pad/Air Mattress - If you're only going to be sleeping in a tent a few nights a year, just buy the cheap air mattress from Walmart. I've had two and use them regularly. They're not great but they're better than sleeping on the ground.
Don't forget a pump. I have a manual pump that I picked up for about $3 on clearance from Walmart; it's big and bulky but reliable. The cigarette lighter plug-in pumps are also pretty cheap (but loud).
If you're curious, I also have a self-inflating sleeping pad from Dick's that'll get you through the night. I also have a really nice, extremely light and compact backpacking sleep pad that I love. These are great for one person, but again, for one person.
Cooking - I'm all about the basics when it comes to camping food. Don't get me wrong, I thoroughly enjoy it and put thought into it, but part of the enjoyment I get from camp cooking is the simplicity of it.
Grill Grate - For most of my life I've simply stolen the grate off of whatever grill is at home. Stack up some rocks and throw the grate over the flames, simple as that. Turn the grub with your pocket knife and if you need to, steal the fast food fork you stashed away in your glove box for no apparent reason and you're good.
Food for thought: This is a very recent point of curiosity to me, but you might want to put some thought into the type of grill grate you use (for everyday life grills in general). https://www.sgs.com/en/news/2018/08/safeguards-11518-bbq-enamelled-grills-can-release-unsafe-amounts-of-heavy-metals-into-food
Propane Camping Grill - If you're camping during a burn ban, you're against campfires in general, or just want the convenience, a propane grill is also great. I had a small two-burner Coleman stove for a couple of years and loved it. I actually used it as my primary cook method for over a year when living in a cabin without appliances.
Cooler - If you don't have a Yeti [cooler] sticker on your lifted truck, do you even outdoors, Bro? I do own a Yeti [Cycle] but I don't own a ridiculously expensive cooler. I do live and camp in black bear country but I have a feeling there's other things laying around camp that a bear would be more interested in. Buy the damn Igloo at Walmart and put the savings into the things you actually need.
Small Necessities
Lighter - Just keep a Bic in your automobile.
Bug Spray - Do NOT forget this.
Hand sanitizer.
Whiskey - Just because. Yes, it's necessary. No, it better not be from anywhere by Kentucky.
MSHA Electrical Tape - Being from Coal Country, Miner's black tape is coveted. While the rest of the world praises duct tape for it’s versatility, Coal Country folk know that miner’s tape is the real miracle worker.
Conveniences
Hammer for tent stakes - 99 times out of a 100 can be substituted by a rock.
Axe - Will be used 100 out of 100 times you have a campfire.
Machete - It's just cool to be able to say you have a machete at your convenience. Also good for clearing undergrowth.
Tin Foil - Baked taters in the campfire is a must for me. I've also made foil 'pots' to scramble eggs over my camping stove.
Multi-Tool - I couldn't tell you the last time I used mine but only because it's such a convenience I don't realize how many ways I've actually utilized it.
Pocket Knife - I've carried a pocket knife since I was a kid, but I'm also full-blood hillbilly. For me a pocket knife is a necessity, not a convenience, but for most folks it'll likely fall under this heading.
Headlamp - Hands-free flashlighting is handy as a pocket on a t-shirt.
Lodge Cast Iron Cookware - Lodge brand is still made in Tennessee and owned by descendants of the Lodge family. The other brands on the shelf are likely made in China, do what you wish with that information.
Small skillets are convenient for eggs or flapjacks. Larger skillets for literally anything you can dream of.
Bisquick Shake n Pour Pancake Batter - Dirt cheap and comes in a convenient bottle that you just add water, shake, and pour onto that Lodge Cast Iron you brought.
Utensils depend on what you're planning to cook. If it needs to handle heat from a fire, pack something that will. If not, just grab a few sporks from KFC on your way. Also, that pocket knife you may or may not already carry goes a very long way.
Cowboy coffee pot (percolator) - If you're like me in recent years, this is less a convenience and more necessity. The cheap Ozark Trail coffee percolator works just fine. Update: I should listen to my own advise. The Ozark Trail percolator sprang a leak at the seam after a season of use.
Toilet Paper - Hey, ya never know if the campground restroom is stocked.
Noncessities (I might have made that word up and if I did, consider it trademarked.)
Portable electronics charger - Depending upon how you plan to use the rest of your time, this could be an absolute necessity. But in the pure case of car camping, it's not.
Backpacking Food - I've only tried a packet of oatmeal pancake mix that was on a clearance rack at Walmart. These things get pretty elaborate for the convenience, but I have no idea how good any of it tastes. Use at your own discretion, but I just stop at the store on the way and buy real food. It's not like you won't have that Igloo cooler within arms' reach.
Backpacking hammock - These were so trendy a few years ago and I can't deny that they're pretty awesome to relax in. I've skipped the tent and only brought a hammock on several occasions.