Technical equipment such as harnesses, helmets, crampons and ice axes will be provided for you but if you have your own it is worth bringing them as you will be more comfortable with your own kit.
2 or 3 pairs of walking socks- proper walking socks have extra padding where you need it the most and are worth getting!
Mountaineering Boots – a decent pair of boots are invaluable but expensive so if you don't already have a pair think about hiring and try a few out before you decide to buy. They need to be rigid enough to take a step in crampon, waterproof, warm and have good grippy soles (some have special rubbery material on the soles for grip on rock)
Waterproof jacket and trousers or sallopettes. As you will be walking or climbing, you will be creating your own body heat, so a waterproof, breathable shell is fine. Padded ski wear is often too warm – it is better to have layers underneath a shell. It is a good idea to have trousers with elasticated bottoms or snow cuffs to stop any snow or dust / rocks from getting inside your boots. For trousers and jackets if it is possible to get material with some stretch in it – go for it.
At least three layers - thin thermal layer or t-shirt made of wicking material rather than cotton next to the skin, a mid weight fleece and a thicker fleece. It is better to have lots of layers so you can strip off going up and pile on the layers when you are cold as body temperature will vary quite a lot as you are walking and climbing up and down. The merino wool thermals made by companies such as ice breaker are perfect.
Extra fleece or sweater
Fleecy trousers or thermals to wear under your outer trousers and / or a decent pair of mountaineering trousers – usually made from a thickish, water resistant stretchy material.
Shorts and t-shirt – lower in the valley and on the first day walk ins to refuges it can be hot so shorts and t-shirts made from good wicking material are worth having. Zip off trousers are sometimes a good compromise!
Gloves, hat, neck warmer or ear warmer. It's worth getting decent warm gloves or mitts. For ice climbing and general mountaineering in snow and ice conditions your gloves need to be flexible enough for you to be able to use your fingers to do things like clip a caribiner. For most summer mountaineering a good pair of fleecy gloves are fine. A 'buff' with a fleecy and a material end is good for head and neck as it can fit under your helmet – or alternatively / in addition a thin fleece hat or balaclava is good.
Rucksack to carry spare sweater, waterproofs, packed lunch, water bottle, climbing kit, ice axe, crampons etc and other bits and pieces. Good idea to put a waterproof rucksack liner inside your rucksack. For mountaineering it is better to have a narrow, hard wearing rucksack, rather than a trekkers sack with side pockets. You will need to make sure there are ice axe loops on it – a 35 - 45 litre sack is about the right size for day or one overnight trips.
Good sized water flask or a plastic water bottle. A Platypus or similar water system is also very handy, but beware, they can freeze so an insulated tube is a good idea.
Thermos flask – the metal ones are best as they can't beak when you drop them!
Sun screen and lip salve with sunscreen
Sun glasses - you should make sure they wrap well round your eyes at the sides to protect you from snow glare from the ground
Goggles – for eye protection in snow blizzards (mainly for winter mountaineering – not usually necessary in summer)
Sun hat or cap for warm sunny days.
Head torch – essential for those early alpine starts and the refuges!
Ear plugs - just in case there is a snorer in your dormitory!
OTHER USEFUL THINGS
Duvet jacket - serves as a good lightweight warm jacket for those cool evenings or frosty early starts.
Gaiters – if your waterproof trousers don’t have snow cuffs, and even if they do, sometimes a pair of gaiters are worth bringing as an extra defence against snow or dust and rocks entering your walking boots!
Camera, spare memory card and batteries.
Pen knife – not essential but it is always good to have a decent knife – mainly for picnics! But it can serve as a tool for repair and maintenance.
A small sit mat or bit of old camping mat - not essential but good for a bit of comfort when picnicking in the snow.
Swim suit – please note that boxer short style swimming trunks are not allowed in french pools.