FF1- WoL (VERY good tank! Can provide solid brv battery to party with second ability, and a small amount of brv, then DOUBLING everyone's current brv with the first. Places unique shield on all allies that absorbs incoming Brv Damage, leaves enemies gaining nothing and protects ally and self brv total. Second gives enemies a lock on debuff that makes them target him, and increases his Evasion and int brv, which his shield and Brv Battery is based on. Lots of ability uses, and a solid HP+ and Brv+, marking excellent longevity. EX increases speed, deals more damage based on current barriers, and restores 20% max Hp. Ex currently paired with Shantotto, EX+ Comes on the first event with Garland, so if you want it now or later, both paired with good units, you are afforded that chance.) Got it
FF2- Firion (Solid Damage and battery, plus healing. Can overheal allies and self with nearly every attack due to Blood Sword buff, and when he overheals, he restores a small amount of Brv when Hp Recovery isn't possible. EX has 100% Splash )
FF3- Onion Knight (Atk Aura and switches between overflow single target physical, and splash blizzard magic. Will be super good once EX+ comes out, and will enchant party and imperil enemies with Blizzard then) Got it
FF4- Dark Knight Cecil OR Paladin Cecil ( DK is a solid damage dealer, using dark attacks and draining his health, but can recover it as well, and can launch. EX launches and deals lots of damage. Has aura, don't no much about that. PAL buffs the party with Brv and Hp Regen and Def, can both Battery and Heal party with either ability, and has powerful Brv+ and Hp+. Most attacks are Holy element, and EX Imperil's Holy, leading to consistently good Damage targeting weakness. Both are very solid in the right parties, but cannot be used together.)
FF5- Bartz (consistent Battery and Brv shaver with both EX and second ability. Must use both abilities once to "Master" them, granting party aura. First is Brv damage dump, second does solid party Battery and fractions enemy brv before attack. EX does practically the same thing, as is fast, making him an effective battery and general buffer.)
FF6- Terra (Damage Dealer, Self Buffer and Debuffer, can do both high amount of hits and charge up her own brave, depending on what's necessary. Bad EX, but good abilities. Not a solid investment right now, wait for rework)
FF7- Cloud (Tactical Damage Dealer, can guarantee a launch with one ability, and guarantee paralysis with the other afterwards, charges Brv a bit before heavy Brv attacks, FIRST EX+ IN CHAOS, lots of powerful self buffs, both good and bad in different cases. VERY good investment, but will be first on banner in Chaos with his EX and Vincent's, so take caution.) Got it
FF8- Squall (Damage Dealer and Splash Expert, can effectively clear waves and deal solid damage to both single and double bosses, One of the First EX+'s, But comes on a banner alongside Ultimecia, an very good character, so waiting is fair.)
FF9- Zidane (Debuff and fast Damage Dealer. Similar to Terra, only physical and faster, with unique debuff and buff, Ex is fast and launches)
FF10- Tidus (Debuff and SUPER FAST Damage Dealer and Brv shaver, First Ability gives him a unique buff that then gives him Free turns when building up Brv attacking and gives overflows in second ability. messy to deal with low buff duration and no way to refresh it permanently, but very useful when used right, EX does 100% to all enemies)
FF11- Shantotto (Heavy Magic Damage Dealer, does extra damage under unique mechanic Rage, is extended by getting hit or using Brv to restore up to the third stack, and becomes permanent after being reduced to 50% or less Hp during combat. Both double HP and Overflow abilities available, EX imperils four elements, Fire, Wind, Lighting, and Dark, Just had Rework Banner with WoL, so if you don't have both, consider it first.)
FF12- Vaan (Magic Damage Dealer, all attacks can gain different element follow ups, can Self Atk up a little with his first, and Def Down and blind with the second one. EX does fire damage and half splash. Sorta outdated and won't be useful until Rework and EX+, not great choice right now unless favorite) Got it
FF13- Lighting (Damage Dealer and Free turn character, after using EX, any break she does gives one free turn for her, cannot trigger consecutively. Switches between a high attack mode using a Non-Elemental attack, and a Brv Regen mode using a Lightning Elemental attack. EX does three Brv-Hp attacks, benefits from max brave before use. Useful, but sort of selfish, other damage dealers can do what she does and more, but much later she will rise to the top. Solid investment either way.)
FF14- Y'shtola (Immensely useful Brv Battery and Delay Character, can restore her own Brv with Brv+, and gives brave based on current amount and Max Brv buff everyone with second ability, meaning full Brv Battery if used right, can brv dump with first ability and delay enemy turn, if Brv not high enough can attack and delay without dumping, setting up Ability two. Very useful EX that can do a lot of things, including fully heal and revive, max out brave, restoring ability uses, and more after EX+, including becoming a free turn. Excellent investment) Got it
FF15- Noctis (Delay, Free turn Damage Dealer, similar to Vayne in some respects. Both abilities become plus versions when used, then go back to normal after being used, and so on. Both abilities, every second time used, makes him act right before the targeted enemy, allowing him to act many more times then everyone else if used correctly. Enemies hit with these abilities get the unique debuff Point Blank Warp, which lowers defense and triggers a follow up Hp attack on the second uses of abilities, with the first ability triggering a launch with it's follow up. EX Hp attacks and gives a unique buff called Armiger, which stacks up to five and raises Max Brv, makes Brv+ and Hp+ into Hp++ and Hp++, the latter gaining a follow up on enemies with point blank warp. Can gain turns quickly, and Advance Ability causes his abilities to turn into their + version immediately. Is coming up soon, so may not be needed, but solid investment.)
Most of these characters are super powerful, and will be solid investments for the future should you be able to MLB them. Since you only get their EX for free, be cautious about spending on characters you don't have other weapons for, and plan accordingly. You can use weapon tokens and orbs to get and max their 15cp and 35cp weapons, so it'll always be possible to max them as long as you get their EX.
For my money, WoL and Y'shtola are some of the best picks, and will be useful for a VERY, Very long time.
Noctis will serve you well if you haven't gotten Vayne.
Squall and Cloud are both coming very soon with their EX+, but Cloud is paired with a less desirable unit, so he's a better pick between the two if need be. Again, WoL is also a first EX+, and is super solid even without it, but ESPECIALLY with it.
Vaan and Terra are not very good investments, as their rework builds their main kit to make them more useful, their EX+ doesn't do enough to extend their longevity and empower their move set. Avoid grabbing unless absolutely more favourable then all other options.
Lightning and Onion Knight are Last Resorts if you already have everyone else, since they both have a very very good EX+ down the line, yet are only moderately powerful until then. Onion Knight comes quicker, but that's still a bunch of months holding onto an EX you may not want to use, so plan accordingly.