As of 2019-03-01, this achievement has become very tedious to complete. While not as bad as it could be, as the achievement is no longer fully upgrade the ship and is limited to only require a "Legendary" ship, this still requires a lot of resources. Unfortunately, there was nothing that I was able to find online that outlined exactly how many resources were required for this achievement, thus here we go. As a result, I have taken the time to gather the requirements for each of the ship upgrade components, including all of the expanded upgrades which are required for this achievement.
Additionally, as noted by the other guides here, achieving Tier 4 on within the mercenary ranks is almost necessary due to just how many resources are saved by reducing the cost by 50%. The numbers listed here for this price reduction were not computed and nearly all were manually verified* for each upgrade in effort to ensure that nothing was accidentally misrepresented. *The first 4 hull upgrades were already purchased but line up with others at similar levels, hopefully these numbers are accurate.
I do not have any good locations for fast farming of resources, my suggestion is to continue to play the game and gather all potential resources that you come across. This means looting all war supplies before burning them, and while a bit tedious walking around instead of fast travel or even utilizing your horse.
The other guides also place a high importance on the tablets as they are a finite resource in the game, however with the Tier 4 mercenary, this specific resource requirement is drastically reduced and therefore does not require the amount of effort needed to track down all of them. I still suggest taking the time to collect them all as doing so will only aid in collecting all of the other resources that are needed to complete this task.
You will need the following resources to achieve this goal:
--Tier 4 Mercenary--Soft Leather:
6021 (leather)Iron Metal:
10515 (metal)Olive Wood:
21296 (wood)Ancient Tablets:
75 (tablets)Obsidian Glass:
1244 (glass)Precious Gems:
Without Tier 4 Mercenary, you will require the following resources:Soft Leather:
13195 (leather)Iron Metal:
19855 (metal)Olive Wood:
42575 (wood)Ancient Tablets:
131 (tablets)Obsidian Glass:
2485 (glass)Precious Gems:
Obtaining Tier 4 saves the following 7174 leather, 9340 metal, 21279 wood, 56 tablets, 1241 glass, 1951 gems, and 250110 drachmae. As commented above, the fact that we do not need to get the [current] top/last upgrade for each ship component is very fortunate as each one costs about as much as the entire Tier 4 achievement set. The total prices including all upgrades are [Tier4/Normal] 38953/79055 leather, 50955/100730 metal, 85823/171625 wood, 75/131 tablets (no additional tablets needed for the final upgrades), 17009/34010 glass, 15118/30230 gems, and 2149565/4298750 drachmae. To put this slightly into perspective, if you have already achieved this, the total for the last upgrades for each component would run you 32932 leather, 40440 metal, 64527 wood, 0 tablets, 15765 glass, 13164 gems, and 1899075 drachmae.
Below are the resource requirement breakdowns for each category:
With the exception of the Fire Braziers, every Level 1 is already unlocked when you first receive the ship. In addition to this, I have included the last tier to show the cost, however it is not needed for the achievement.
Tier 4 Mercenary Resource Requirements:
Normal Resource Requirements:
-All counts were gathered on 'Nightmare' difficulty; while I don't believe that this would change from difficulty to difficulty, I figured it best to note, and if there is a difference, this would likely require the most resources.
-When buying resources at the shops [Blacksmith], resources have the following cost.Leather: