- Estimated achievement difficulty: See below [Achievement Difficulty Rating]
- Offline: 67 
- Online: 0
- Approximate time to 500: See below [Estimated Time to 100%]
- Minimum number of playthroughs needed: 1 [for FF X]
- Missable achievements: Yes [see below]
- Does difficulty affect achievements: No
- Unobtainable/glitched achievements: No
- Extra equipment needed: No
DLC: Final Fantasy X
- Difficulty: 5/10
- Time to 500: 90-110 hours
- Missable: Yes - "Master Linguist"
- Unobtainable: No
DLC: Final Fantasy X-2
- Difficulty: 6/10
- Time to 500: 70-100 hours
- Missable: Yes - 11 [refer to roadmap]
- Unobtainable: No
Final Fantasy X DLC
FINAL FANTASY X tells the story of a star blitzball player, Tidus, who journeys with a young and beautiful summoner named Yuna on her quest to save the world of Spira from an endless cycle of destruction wrought by the colossal menace Sin.
The only missable things in this game are related to the "Master Linguist" achievement. There are four Al Bhed Primers (numbers 19 through 22) that are only available for a certain amount of time and must be obtained as soon as you come across them. If you'd like to use a walkthrough, the website Jegged has a good one, and I used their version of the FF7 guide for great success as well. The missable Primers can be found on pages 20 and 22 of the walkthrough, so pay special attention at that time.
Step 1: Get the Airship
The main task of this step will be to work through the story. However, pay attention to a few things along the way. Always collect the Al Bhed Primers (most specifically the four missable ones I mentioned above), the Destruction Sphere in every temple (see "Feel the Pain" for more info on that), and the Jecht spheres as well. You can also work on stealing with Rikku and bribing enemies. There are a number of other optional things that will get cleaned up in the next step. You don't really need to go out of your way to do anything now.
Step 2: Complete All Side Content
Assuming you got the four missable Al Bhed Primers, at this point you should have smooth sailing to the completion (though the journey will be long). You can continue with the story until page 30 of the Jegged walkthrough, just prior to the final dungeon, and then knock out any remaining achievements you have left. There will be optional superbosses, leveling your characters, getting all the special weapons, etc. Check what you're missing from the guide below and set to work knocking them all down until you only have three achievements left, which should be for the final two story bosses and the epilogue movie selected from the main menu.
There are two suggested methods for completing all the side content as far as actually getting strong and beating enemies. You can either abuse the Yojimbo summon which will auto-kill just about any enemy but is frankly a bit complicated to use (info on that can be found here), or just level your characters and get your stats as high as possible (you can see which enemies in the arena give which types of spheres here). Most people consider Tidus, Wakka, and Rikku the best end-game party, though others will swear by Auron or Kimahri as well (usually in place of Rikku). While there is an achievement for maxing out your grid sphere, this doesn't necessarily mean you'll have max stats, which takes a bit of extra work. See "Perfect Sphere Master" for tips on this.
Step 3: Complete the Game
At this point, you should only have a few story related achievements left tied to pages 31 and 32 of the Jegged walkthrough, and the achievement for watching the video from the main menu.
Step 4: Watch the Eternal Calm Video
You can technically do this right away when you start the game, but I'd suggest leaving it until now because it is a video that explains the events that take place between FFX and FFX-2. For new players, this is obviously best watched after completing FFX.
While this is a very long completion, and will take quite a bit of preparation for the superbosses which can be fairly difficult, overall it is not too hard to do since only a few minor things can be missed. However, you'll want to make very sure you don't miss them or you're in store for a second playthrough just for one achievement. Good luck!
Final Fantasy X-2 DLC
FINAL FANTASY X-2 returns to the world of Spira two years after the beginning of the Eternal Calm. Having been shown a mysterious but familiar image in a sphere, Yuna becomes a Sphere Hunter and along with her companions Rikku and Paine, embarks on a quest around the world to find the answers to the mystery within.
Step 1: 100% Run
FFX-2 is a bit different from X in terms of gameplay and pacing. The game is split into chapters, and each chapter has specific actions that must be taken to work towards what the game considers "100% Completion" based on talking to specific characters and completing side-quests. If you follow this guide as you play, and ensure that your % matches the guide after each thing you do, you shouldn't have too much trouble getting the "Sweet Perfection" achievement in this step. If you don't, you can use Step 2 and a NG+ run to get anything you missed.
Note: One thing that guide doesn't cover in depth as it goes is the "Public Relations" side-quest. It is mentioned in the beginning, and it is mentioned again when you should start it, but then you are left to your own devices in finishing it. Make sure you check the bottom of the guide each time you come to a new location to get PR points until you get over 400, then you can ignore it for the rest of the game.
Note 2: Another minor thing it doesn't mention is when to do the "data dealer" trick to get a ton of money. See "Millionaire" for info on that. Missing it won't ruin your playthrough by any means, but it does make things easier.
The 100% Walkthrough will get you all the dresspheres, some of which are used for miscellaneous achievements (using Mix, learning Blue Bullet skills, etc), and it will also get you the achievements tied to O'aka's debt, unlocking the Ruin Depths for the Amazing chocobo, etc. Basically, follow the 100% Walkthrough and be mindful of the achievement list itself, and you'll be able to get everything done in this step. You can combine the 100% guide with this walkthrough for the story itself to stay on track.
Step 2: Shinra's Bestiary
One of the more time consuming parts of the achievement list requires that you see every enemy in the game, as well as seeing them in their "oversoul" state which occurs once you've killed a certain number of enemies in that species. The important part to note in that last sentence is the word "see" because you don't actually need to kill the enemy to get credit toward the bestiary.
See "Monster Master" for some more specific info on this achievement, but be aware that as you play through the story, it would be in your best interest to never kill an oversouled enemy unless you have to (this would only apply to bosses and the Mega Tonberry enemy). Otherwise, you should escape from battles after killing any regular enemies, leaving the oversoul enemy alive so that its species will remain oversouled, and any future enemies in that same species will count toward the bestiary as well. This will severely cut down on your grinding later on.
Step 3: Mop Up
If you missed anything in the step above, you can begin a New Game Plus (NG+) playthrough which will carry over all your data and inventory. The only thing that resets is your character level. Run through the game again taking note of what you missed to mop up your 100% completion and all but the six achievements tied to Last Mission.
Step 4: Last Mission
Last Mission is a separate game mode accessed via the main menu. See "Giant Tower" in the guide below for tips on completing all the floors of this mode and unlocking your last six achievements. This part will only be 6-10 hours of your completion.
FFX-2 is a bit of an easier completion compared to FFX, both in terms of difficulty and time investment. However, it has many more missable achievements, so it's important to be thorough with the guides if you intend on only doing one playthrough. However, the addition of NG+ makes cleaning up anything you missed much more simple than having to do everything over instead. The Last Mission mode adds a nice extra element, though if you're not a fan of roguelite game modes, it may be a bit annoying. Overall, this is a good story and decent complement to FFX.
[XBA would like to thank The Pants Party for this Roadmap]