This guide applies to all 3 of the achievements for which you have to play on all of the locations in the game combined.
The important issue with these achievements is that half of the locations on each island can be unlocked only with Gems, sometimes a few of them, but most of the times a lot of them. This is how I farmed Gems: I waited until the time when the Pack (Daily) challenge would change to a new one, that would be in the middle of the night and when it did, I would complete it, let the game run and then go to my PC's time and date settings and go back 2 hours in time. Then I went back in the game, paused and hit the Xbox Sign In button. Back at the map, in Pack Challenge, now the current day's challenge will be available again for completion, rewarding you every time with whatever rewards there are that day. Now, you can repeat that challenge as many times as you can (stand) for 2 hours and finally set your PC's time correctly (sync with Windows time server), signing back in again through the Pause menu. I got this idea from Crimson Drifter
and varied it a bit. The reason why I set the clock back only 2 hours is because I found that if you set the clock back too many hours in the past, then your pets will appear as being tired and sleeping, even if you have fed your pet a Super Treat. However, you can repeat this process every day when the Pack Challenges change. While doing this, you will also get a ton of Coins through the rewards from the Pack Challenges that you repeat over and over.
Alright, so when you have enough Gems to unlock all of the locations on the island that costs the most, which is 480, pause the game and upload your save to Cloud.
Now, unlock all of the locations on one of the 3 islands and play a Free Play session in each zone to get the achievement for that island. After that, you go ahead and download your save from Cloud (through the Pause menu) and repeat this procedure for the 2 other islands. This way, you use the same batch of Gems to individually unlock all the locations on each island and after each of them you'll get the corresponding achievement. Of course that every time you download your save from Cloud, the locations you just unlocked with those Gems will be locked again, but you'll have your gems back and the achievement unlocked.