Some of the coins are pretty difficult to get but there are enough to upgrade yourself until your able to jump across the map to a little building in the top left corner. It'll take you to the next and final level where you get the arm cannon gun.
Oh ok, how do you use the coins to upgrade yourself? Do you have to interact with that thing in the building again?
Yes, and on level 2 there are 2 trade terminals one increases your health the other increases movement speed and jump height.
