2. What is the most appropriate clothing to take on a trip to Iceland?
Usually people bring a lot of clothes, which is not always efficient. The essential thing is to protect the extremities. Good socks (and shoes), gloves and cap. You should bring a windbreaker jacket and a thermal vest. These garments are essential. Many pieces of clothing are not always the most suitable. Thermal and polar clothes are efficient.
As climate instability and wind is a characteristic of Iceland, with gusts of different spots, the umbrella is not advisable. Bring a long raincoat or a "poncho".
Suitable footwear is mandatory as most fractures and twists are due to inadequate footwear. The sole must be rough and never smooth. High heels are not suitable for a trip in Iceland. Use Footwear/Mountain Boots for hiking/trecking.
Don't forget your towel and bikini/bathing suit/shorts as geothermal pools/baths are one of Iceland's great attractions (e.g. Blue Lagoon). Be accompanied by flip-flops.