Champion of Ivalice
Ah, the coveted Platinum trophy, which requires you to get every other one in the game before this will ding. This will take you a good while to get, as there are a few trophies that will be roadblocks, either from difficulty or because it takes a long while to do everything. These include killing at least one of every enemy, learning every magick/technick, performing every Concurrence, fully exploring every map and finishing Trial Mode. If you need a time estimate, then it could take upwards of 100+ hours to get this platinum.
Champion of Ivalice
Collected all other trophies.
General Combat/Exploration Trophies
There are a few trophies that you will undoubtedly get as you just play through the game during general gameplay. This includes the ones for attacking, casting magicks, using technicks, stealing, defeating a certain amount of enemies, and taking a specific number of steps. The only one that might not come naturally is stealing 50 times, but you should be stealing from most enemies in the first place, especially in the beginning of the game, which will help you procure more loot and items.
Used Attack 300 times.
Cast Magicks 200 times.
Used Technicks 100 times.
Successfully stole 50 times.
Defeated 500 foes.
Took 50,000 steps.
As you kill enemies of the same species, you will notice a counter increasing in the bottom right corner of your screen. This is the chain counter and it will drop to zero whenever you enter a safe area (where you control only Vaan). touch a Save/Gate Crystal, or kill an enemy of another species. The biggest benefit of doing this is that at certain intervals, the Chain Level will increase, improving the odds of obtaining loot. If you plan to farm anything, this trophy will likely come naturally, as some of the best drops in the game involve upping the Chain Level to improve your chances of obtaining said loot.
Getting a 50-chain is not too hard, as there are plenty of areas where a lot of monsters of the same species will spawn. One of the first spots you will come across is in Lhusu Mines during the main story, in the Shunia Twinspan area. On the bridge here, there will be a bunch of skeletons. Make a pass up and down the area, as they will spawn a bit erratically. Once you're done with them, you'll need to head south to Transitway 1 (make sure you're holding R2 to flee, so you don't accidentally kill another enemy), to Oltam Span and back again to respawn the skeletons.
There are other ways and methods of doing this, such as setting gambits to only attack specific enemies, like fire-weak ones in an area abundant with those kinds of enemies (as long as there aren't other fire-weak enemies in the same area). Another area where you might get this is in Ogir-Yensa Sandsea, as there is a Rare Game that requires you to kill one-hundred Urutan Yensa to spawn (don't need to chain, but it's easier to keep count). Other good enemies to chain include Mirrorknights in the Feywood, Dark Lords in the Stilshrine of Miriam (after defeating Zeromus), the Jellies in Henne Mines, and the Abysteels in the secret area of Henne Mines. If you farm for money and levels, while not randomly killing everything in your path, this trophy should come naturally.
Completed a 50-chain in battle.
Loot/Gil Related Trophies
There are three trophies in the game that center around loot, acquiring enough gil and spending a certain amount of gil. The majority of enemies in the game will typically drop loot whenever you kill them, but you may also steal loot from them or via another method (the technick, Poach). This loot can then be sold to vendors across the game for gil, and is your main way of earning gil in the game, as enemies don't drop gil upon their defeat. As you progress further into the game, you will find loot that sells for more gil, which will make the 100,000 gil trophy easier to obtain.
So, what do you have to spend all of your hard-earned gil on in the game? Besides new equipment, you can also buy items to use in battle (ex. Potions), new magicks and technicks, as well as Bazaar bundles. The last on that list are unlocked by selling specific pieces of loot in certain quantities, with a select few items - the Monographs - unlocked by various other methods. Some of these bundles are very expensive, with one of the best swords in the game costing a whopping 600,000 gil. So, if you are looking to unlock some of the best equipment in the game, you will be spending a lot of gil.
Acquired 100,000 gil.
Spent 1,000,000 gil.
Sold 1,000 pieces of loot.
Clan Points are given to you once you join Clan Centurio in Rabanastre, which can be done as soon as the beginning of the game. Basically, every single monster in the game will yield Clan Points upon defeating them, but they don't show how much, as the actual value is hidden. The more lucrative the monster, as well as its strength, the more CP you will typically receive, with Rare Game and Hunts giving you more. 500,000 Clan Points is not a whole lot, really, considering all of grinding that is needed for other trophies.
Obtained 500,000 Clan Points.
For these trophies, you need to have an average party level of 50 or higher, as well as earn 48,000 License Points (LP). You have six party members and you need to take the sum of all their levels, then divide them by six. When this equals 50 or higher, then you will receive the trophy. You will unlikely get this trophy during the main story, so it will take some extra grinding to get it. There are a number of places where you can grind to your heart's content (only those after the main story will be listed). Remember that the Embroidered Tippet accessory will double all experience gained, so make sure you equip three of them on your active party members.
One of the first spots is after defeating Zeromus in Throne of Veiled Gods in the Stilshrine of Miriam, which will now be populated by Dark Lord enemies. While it may not be the best for experience, you can grind here for Gil, as the Dark Lords can drop Blood-darkened Bones, which sell for 1,435 Gil a piece. Another horde of undead can be fought in the Overlooking Eternity area of Nabreus Deadlands, which is accessible by finding the hidden path in The Slumbermead. You will find a lot of Dead Bones here, so don't forget to use something like a Holy Lance or have a gambit set up to use Curaja on them.
By far, the best experience spot will open up once you get 10 Espers, as you will be able to unlock the secret area of Henne Mines. Once you have the requisite number, go and speak with Geomancer Yugelu in Jahara to open up the secret area, which is accessible from the Ore Separation zone. You will probably want to be around level 55-60 in order to come here, as the enemies do a lot of damage. Make your way to Pithead Junction C and flip the switch there to find a bunch of Abysteels dropping down on your head. The Abysteels are considered undead, so they are susceptible to your curative magicks. In fact, the easiest way to take out a group of them is by using the combo of Sleepga and Curaja.
The only problem with this is that only certain classes learn each of the above magicks. Curaja is only usable by the White Mage and Knight, with Knight requiring Hashmal, while Sleepga is only accessible to the Black Mage and Red Battlemage, with the Red Battlemage requiring Cuchulainn. You could also use Disable on the Abysteels, which can be used by the Time/Red Battlemages. You would basically set up gambits to Disable/Sleep undead, then target those ailments with Curaja. Don't forget about your own safety, too, as the Abysteels are quite strong.
Raised your party's average level above 50.
Earned 48,000 License Points.