Explanation in Maplestory:
This build requires the least mesos at early 4th job out of all three common builds. Mastery adds a considerable amount of damage to every skill a bowman has for how inexpensive it is.
Common points to all Bowmaster builds:
1 Hurricane and 2 Sharp Eyes are obtained at 120 due to the fact established in the bowman FAQ that level 1 Hurricane and any level SE is better than max Strafe and any level SE. 1 point in Bow Expertise is obtained the level after, as level(Maplestory powerleveling) 1 SE has an infuriatingly short timer (which is why Bow Expertiset is not gotten at 120) but yields a substantial increase in all attacking skills damage for only one point. Level 10 SE is a standard expectation of 4th job bowmen, as the timer is at a decent length and adds a decent additional activation rate.
Zakum runners in GMS expect level 10 SE, and participating on Zakum runs allows a player to build up funds to purchase other mastery books. 1 Phoenix and/or Concentrate is usually gotten somewhere before 140, for fun. The last 3 points of mastery only add one attack and zero mastery %, so these three points are better spent in SE, Hurricane, or MW, as each add more damage than 1 atk point will. The 3 final points in expert can be added afterwards. Likewise, the last 9 points in hurricane add less damage than 9 points in SE or Bow Expertise will, and are usually added after SE gets to 29 and Expert to 27.