Stove and water filtration
If you plan to cook meals during the expedition, I recommend taking a gas stove with gas cylinders. Being made of aluminium, they are very light and available in all capacities, starting from 100 ml. However, if you are travelling by plane, you will not be allowed to take gas cylinders. You can only hope that compatible gas cylinders will be available at your destination. This may pose a problem, as there is no universal way of mounting gas cylinders to the stove. I think that globally, the most popular stove producers are Coleman and Primus.
Another solution is to take a petrol stove. I recommend MSR and Coleman products. You can even use gasoline from a petrol station. However, this type of stove is more troublesome to use.
There are available also dual fuel stoves where you can use gas cylinders and liquid fuel. Such stoves are produced by MSR, Brunton and others.

It is also worth having something that will allow you to drink water from streams, lakes or puddles - in emergency situations. Although water purification tablets can be used, they tend to make water unpalatable. The best solution is a small, silver-based ceramic water filter. I recommend products from Katadyn - especially the Mini model, weighing just 210g, and the Pocket model - probably the best filter in the world, weighing around 550g.