I assume you will be going hiking or climbing? I suggest you bring some gear so! In relation to gear that is specific to camping, you need to consider where you will be camped and for how long it will be. If you are going camping in the wild what you will bring might be quite different to what you would bring for using a campsite. Some universal items:
Sleeping Bag
One season sleeping bags are fine in summer, (that being the one season). For camping trips members are advised to bring bags with good insulative properties. In practice this means a good quality 3/4 season bag. Bear in mind that the majority of the time in Ireland it's fairly chilly to be sleeping outdoors. There is no rigorous standard that is applied to the rating of sleeping bags. The "comfort" and "extreme" temperatures are based on standards that vary between manufacturers. In theory you can sleep in a comfort 3 degree bag in your boxers and shiver all night long fully clothed at -20 degrees in a -20 degree extreme bag, at -21 you stop shivering and promptly die. Some questions for the know-all shop assistant: Was is windy when they tested the bag? Was the person fat or thin? How comfortable were they at the comfort temperature? Who knows, shop around and ask your mates.
Tent
Don't forget a tent! Obviously you can share a tent between a number of people. You can buy really cheap tents from Lidl, Argos and Aldi. More expensive tents are lighter, more weatherproof and more durable. You are looking for one with a good ground sheet. 5000mm water column ground-sheets are fine and will work well even over a number of rainy days. Always try to get a model with a flysheet that is separate to the tent part and make sure that they don't touch each other when the tent is up. Look for a tent with a porch if possible, it makes things handier on trips where you have a lot of gear. You can cook in a porch too. Things will always get damp even if you spend hundreds of Euro.
Cooking Equipment
If you plan on eating you will need to cook your own food. Stoves can be bought in any camping shop - look for a nice portable one, not the "happy-camper" type that look like someone stole the top of their cooker and put it in the back of the car. You're looking for either a gas stove with a remote burner such as an MSR "WindPro" or a petrol stove like an MSR "WhisperLite". Avoid the type of stove that requires you to balance a pot on top of a burner on top of a big gas bottle, things have moved on a little. Get one with a tube, a "remote canister" stove, (much safer). If you have a Trangia or another archaic relic, leave it at home, beside the bin preferably. Petrol stoves are as powerful as gas ones and have all the advantages of remote canister gas stoves as well as being a lot cheaper and running on almost anything, (including whiskey - perish the though). They are slightly bulkier, heavier, smellier and dirtier than a gas equivalent but are better if you don't want to bother with having to deal with the hassle of getting gas abroad.
You will also need some pots or mess tins and a lighter. There are vast numbers of types of pot, pan and tin out there. Stay away from plastic handles and cast iron. Going to a campsite? Check if disposable barbeques are allowed on site before using them. They're very handy for cooking meat.
What will I cook? Believe it baby anything is possible. You name it, all you need is a little luck, an bit of patience and some imagination. Dolmio and pasta is handy for a day or two but after that you'll be bored and constipated. Contrary to popular belief cooking while camping does not take long, in fact if you're set up properly and switched on to cooking you'll produce food quicker than at home. Remember the burner on an MSR has about four times the heat output of a domestic cooker. If you want to spend the rest of your life watching pots then try a Trangia.
Bring detergent and scrubbers if you're in a campsite, forget about it if you're in the wild. Don't even dream of polluting a watercourse!
Water Container
It's a good idea to keep some water with you during the night in case you're feeling dehydrated. A small container is always useful for the cooking water as well.
Torch
It has to get dark sometime. You should always have a head torch out hiking or climbing anyway.
Toiletries
Bring all your normal stuff if you're at a campsite. You should only need toothpaste, a toothbrush and soap, (Dove if your clever - doesn't dry out your skin like soap does). Shampoo and all the rest is unnecessary if you're sensible. If you're camping on the wild you'll be taking none of this of course, don't even think about it...
Insect Repellent
This deserves a special mention because generally we think of mosquito and the like when thinking about bug spray. In Ireland you will be eaten alive by midges in the cool dry evenings of April May and June, (good climbing weather). If you are camped close to water, a swamp or a bog then expect an attack.
Clothes
If you don't bring spare clothes you will smell and people will start ignoring you. Also you are bound to get wet at some stage during a trip.
Money
Always handy for paying for things.