At this point in the game, there are a crapton of 4* abilities available and not all of them are really all that great. Here is a short list of 4* abilities that I feel are worth creating and honing. Just as a general disclaimer: Though I did try to make this list as generic as possible (no cheese strategies, etc), like all things FFRK, overall usefulness of a particular ability will depend on your party makeup, abilities available, SB’s, and so forth. I have a tendency to lean towards physical damage parties. My typical party makeup is: 1 Healer, 1 Hybrid Black Mage, 1 Cloudblade Spellblade, 1 Support, 1 other physical. I don’t use summons all that often, thus the reason why none are listed.

Support & Healing Abilities
If I had to choose an ability to create first out of everything listed on this page it would be Magic Breakdown.

Magic Breakdown
Unlike physical damage, magical damage cannot be mitigated by backrow parties. Magical damage is also heavily used in the and needed to avoid being instagibbed in many of the higher level boss fights.

Shellga & Protectga
Yay mitigation. Don’t bother honing either of these past R2. One cast lasts for quite some time. There are other mitigation options in the form of certain relics, bard abilities, etc. Regardless, I would say that it is worth creating these abilities. Depends on your party makeup though.

Steal Power
If you can fit a character with a high thief skill into your party, Steal Power superior to Power Breakdown. In addition to a longer duration, it offers a 50% attack buff. Keep in mind however, that this ability does not in itself do any damage and that the buff does not stack with any other attack buff (such as Planet Protector, etc). Because I have Aerith pimped out with Planet Protector, I usually end using Power Breakdown (mostly because I already had it honed to R3 by the time Steal Power was released :/).

Armor/Mental Breakdown/Steal Armor
Steal Armor > Armor Breakdown. Obviously, use Armor Breakdown for physical parties and Mental Breakdown for mage parties. If you are a completionist or have spare orbs available, these abilities may be worth getting. Otherwise to be honest, all of these abilities kind of fall under the “filler” category.

Curaja
If you use a character with a low mind stat for tanky healing (like Pecil for example), then Curaja is to get a decent heal of any sorts. Otherwise, I have never felt the need to use anything higher than Renewing Cure or Curaga on any of my white mages.

Elemental Damage
The elemental strikes are included in this category because of the role they fulfill and the fact that their orb usage heavily overlaps with the -ja/-ga spells. Keep in mind however that these are physical abilities and that damage output is attack based.

Waterja
Of the elemental spells, Waterja is the least resisted, has the fastest cast time, and is fairly easy to make.

Bioga/Thundaja/Firaja/Blizzaja
The power creep is real. There will be a point/already are certain bosses where -ga spells simply do not put out enough damage. The order at which you craft and hone these abilities is up to your preference I guess? Bioga seems to be pretty easy to farm, not very often resisted, and a weakness on many bosses. On the other hand, it does have a lower damage multiplier than the other ja spells so many only be a higher priority if your ages already hit or are at least close to the damage cap. I personally use Thundaja a lot so I chose to hone that one first (magitek + all mechanical things are weak to thunder damage).

Diaga
I would argue that this ability may be worth crafting first along side Waterja. Being a white mage spell, it doesn’t use any of the same orbs as the other -ja/-ga abilities if I recall correctly, so it should be fairly easy to craft and hone; As long as you have Shellga and Protectga crafted that is as both of those spells should take precedence.

Ruinga
Non-elemental AoE damage. Ignore Quake, use Ruinga. Great for AoE bosses and nuking Daily Dungeons.

Thundaga/Firaga Strike
Both of these abilities are in the same boat as Thundaja and Firaja.

Physical Damage
I personally have a preference for Dismissal and have used it quite a bit. Pound though is decent for combat characters with a limited selection.

Dismissal
It’s like Pound damage wise but has a chance to interrupt. Celerity isn’t that uncommon of a skill so Dismissal it usually pretty easy to squeeze in. It doesn’t however have a great proc rate, so unless you create and hone multiple copies it may suffer from filleritis like Pound. If I had to choose between either Pound or Dismissal: Dismissal.

Pound
Straight up single target physical damage. Pound is a combat ability so it is widely usable. I don’t think this is stated anywhere on the actual ability but it has a 100% hit rate so no missing even when blinded! On the downside, Pound is kind of a filler spell at best: It only does 15% more damage than Launch and doesn’t really do anything special (no buffs or debuffs). It also needs to be honed to be useful.

Bladeblitz/Yukikaze
AoE physical damage. Great for trash clearing and AoE bosses. If you have a Samurai that you drag along often (such as Sephiroth), I would choose Yukikaze over Bladeblitz for the chance to blind all. Keep in mind that both of these abilities require Greater Power Orbs, which complete with the Breakdowns.