After many researches about gear, I've come to a conclusion...

GEAR IS EXPENSIVE!

So, I tried my best to save money, in order to make my trip last as long as I want to, but withoput taking any risks.

My allies for that mission : 

Le bon coin : a gold mine for second hand gear (almost new, and much cheaper). It's a french site but you all have the equivalent in your countries.

Sportpursuit.com : private sales, mainly sports equipments. Delivery throughout Europe

Privatesportshop.fr ; private sales, mainly sports equipments. Delivery throughout Europe

Decathlon :  Decathlon is a French company but has 1038 stores throughout the world. The quality of products is very good with pretty affordable prices.

Aliexpress : It's a chinese website on which I bought many small things for very few money. I decided not to buy the things I consider important (tent, kitchen...) eventhough the reviews are petty good.