Recommended Lists of Equipment / Gear / Tools to take with you:

FOR 4x4 Car / Quad bike ride (1 day ride):
GPS
Insulated water bottle (keep cool water)
Drinking Water and non drinking for cleaning 
Snacks/juices
CoolerBag
WalkieTalkies
Hat for the sun
Bandana for dust protection
Sunglasses
Sun protection cream
Swim Suit for Summer
Basic Snorkeling equipment (to explore crystal waters)
Boots/Trekking Shoes
Toilet paper
Wet antibacterial tissues
First-aid kit
Spare clothes and shoes

General/Basic tools:
Tyre pressure pump (Air-Compressor)
Power Straps (shiappani ->for pulling car/bike)
Ropes
Knife
Tighten clips
Duct tape
Battery starter kit (πόλους)
Power Inverter (12v to 220v)

Camping 2-3 days - Additional items to the above lists:
Camping tent (Tent indoor light)
Sea/Beach Mats - to set in front of the camping tent
Air Bed with 2 sheets
Camping Chairs and small table
Water Storage Container - minimum 20L
Flash Light (led water resistant recommended)
Frappe kit
Clothes peg (for hanging clothes - μανταλάκια) 
Shampoo
Sun protection cream
Mosquito repellent spray (apply 10 min before sunset)
Mosquito Electric Killer Zapper
Sunglasses
Beach towels x 2
SwimSuit x 2
Sandals
Toilet paper
Wet antibacterial tissues
Basic Snorkeling equipment
Volley Ball
....more soon