first : do it the main quest ( on your alt chara too )
second : grinding with black spirit mode or sleep mode if u have free time hunt more violent monster on field.

third : this is the last n the best way...
but first u must build node on your camp n riase your node level for more reward...
but if u don't have much worker just place around 1~3 on node for raise your node level...
remember on node, sometimes appear bonus node.
on bonus node several gifts available.
example : Boss Stamp
Ancient ruins tablet
Black stone
Black Pearl