Getting to the max level in Atlas is pretty easy if you know what to do. For example, you can try to get things done by killing animals. In this case, you must pump at least to level 4 and make a bow with at least 50 arrows. Now go looking for alpha creatures, because they give a lot of experience.
Level 4-8: kill alpha boars (reaching level 8 will only take a few minutes).
Level 8-20 +: kill alpha rattlesnakes.
If you have a sloop, the process becomes even easier. According to some players, treasure maps give a huge amount of experience - for example, one such map gives 2 levels of pumping at once at high levels. Please note that the amount of experience depends on the quality of the treasure map.
How to build a sloop
Step 1: unlock the Ship Carpenter skill (via the Construction and Mercantilism skill tree).
Step 2: use the forge to build a small shipyard (you need 240 fibers, 105 stones, 420 straw and 840 wood).
Step 3: place your Small Dockyard along the coast of the island where you settled (the place should be deep enough, but not too deep).
Step 4: Build the frame of a sloop in the shipyard (120 fibers, 12 metal, 220 skins and 140 wood).
Step 5: build whatever you need (one deck, some wood plates, some wood ceilings, etc.).
Step 6: finally, build the steering wheel and middle sail.
