The thing that makes camping miserable is being cold, take a fleece or hoodie to wear in the evening/mornings/midnight loo visits take a hat to keep your head warm/stop small insects biting you head/cover up bed hair for morning toilet visits. Long socks and if keen flip flop wearer toe socks. Take a blanket to wrap yourself in when you start to feel cold.
After years of camping I have ended up on a self inflating mattress from a company called Alpkit (you can only buy direct from them) they are well made a considerably cheaper than other brands who supply similar quality of mats. Me and My OH have one each which we cover in a double sheet to keep them together. I find a self inflated mattress that has a puncture which you can't fix is still sleepable on but a night on a flat air mattress it a different story!
If you choose air mattress I recommend buying a cheap foam mat to put underneath to insulate you from the cold. And buy extra bungs in case you loose one and a repair kit in case it breaks, don't forget the airbed pump!
On the subject of sleeping bags, if like me you get cold a double sleeping bag may not be the best idea as with two people sharing the cold air has more chances of getting in, if you do feel the cold go for mummy style, if you are only planning summer trips buy a cheaper bag and take a blanket. If you buy a sleeping bag and find you are still cold try a sleeping bag liner as this will make it warmer. Defo take P.J's and warm ones too, I quite often sleep in my thermal undies.
Buy a repair kit if you tent doesn't come with one and take a roll of duct tape to temp repair fiber poles if they split (you can also get replacement poles, be aware they may need to be cut down to the right size for your tent (having done this the wrong way, I recommend strongly you cut your poles before you go away on your trip!). Dont forget the pegs! If you enjoy camping but are getting fed up with bending your pegs invest in some rock pegs (saved many arguments with old OH) they are brilliant highly recommend.
We have three cool bags a big one, a smaller one (which we put inside the big one for extra insulation) and a rucksac one for picnics during the day. I have ice blocks that I have named with a corrector fluid pen (it has lasted for years). It is a good idea to take some plastic bags and a permanent marker as some sites have a communal fridge and its the best way to mark your food items.
Easy food is defo the way forward especially if you haven't been camping before, it is traditional in our family that the first night supper is pasta (don't forget to take something to strain your pasta)and sauce cause it is quick and simple. Anything in tins (as long as you remember a tin opener!) is also good and if going for the weekend frozen precooked meals such as chilli can work to keep things cold in your cool bag and be a quick and simple supper. Think about how many pots and pans you need to cook your dinner compared with how hobs you have (we only have one!).
Other food items to consider, oil (we forgot to take some on our last trip, oops), All in one coffee sachets (in case you forget the milk), herbal tea (ditto if you forget the milk), packets of tommy K, brown sauce and mayo pilfered from a local eating establishment, an all in one box risotto kit.
Having used all kinds of water carriers I recommend the square plastic jerry can style ones which come with a tap attachment, they last longer and are easier to pour from and are less likely to have that horrid plastic taste compared with the soft fold able carriers. A large thermos plus one water bottle per person is also useful when weather is hot.
Don't bother with the traditional metal camping cups bring a china one, they keep warmer for longer and are more pleasant to drink from.
Take croc's or flip flops for the shower as you may need to wear them whilst in the shower. make sure you have a bag to take to the shower so you can hang it up on a hook and keep all you clothes off of the potentially wet floor.
Fold able crates can be great for storing things in to whilst away. And cheap towels are a god send if you have a wet weekend (mine a brown from poundland they never miss a trip). I also recommend a 'camping box with all the essentials in the garage/loft/cupboard, means you have less to think about you can chuck it in the car and go.
Another recommendation is to buy or make a footprint for your tent, it is basically a tarp cut to the size of your tent which will keep the bottom of your tent clean and make it easier to fold your tent up and stop it from getting it filthy when rolling it up in a muddy field at the end of your trip. Once you've put the tent away you can fold the footprint muddy sides together and worry about cleaning it when you get home. Many Tents have footprints you can buy in addition to you tent but you can also go into your local builders merchants and buy a tarp and cut it to your needs (it must not stick out from underneath your tent or it will collect water, cut it slightly smaller).
ukcampsite has a list of camping essentials and user reviews on loads of campsites, other websites are available (pitchup is also quite good).
Phew, I hope that this essay is helpful.
Enjoy your camp trips.
F&T x