This will be quicker to do in a sloop with a low level gold hoarder level, or have a friend with a low level gold hoarder level. The lower the better as they will have less maps and riddles which will also be closer to you.
Pop a gold hoarder voyage down, mark down the island on the map. Once you are at said island if it is an x Mark's the spot you have 2 choices,
1: find and dig it up if you need the cash.
2: hit the spot with your shovel and leave it mostly buried and leave, you do not need to fully dig up the chest to finish a voyage.
If it is a riddle and you are having trouble finding some locations you can google it or download the sea of thieves companion app on an android phone. (Not sure if there is such an app for apple phones)
The app does show you all locations for riddles and much more.
Once you completed the voyage slap another one down. Once you reach a gold hoarder rank that let's you obtain a title... DON'T TOUCH IT. Leveling it up will give you more islands and chapters per voyage. You can always leave the titles alone until you get this achievement.
If you happen to find a message in a bottle that is a riddle or x Mark's the spot, ignore them as they do not count towards this achievement.
That is all I can reccomend to you all. Happy sailing!