A standard nuking set if fine for Dynamis, but for more Kings/ZNMs what have you you should try to build a resist set. I would recommend trying to reach the 120 INT threshold for this and then abide by a elemental > MAB hierarchy. This is all dependent on what exactly it is you're fighting of course and normally a BLM would adjust gear accordingly. But since you're just trying to build one fairly standard gear set, I would say to just gear for the worst case scenario. For example, for high level HNMs you will find your AF hands > Vicious Mufflers. Whereas if you're nuking stones the reverse would perform better.
There have been some good suggestions by other people already, but off the top of my head I'll list some items you can consider if your fund allow:
HQ Staves when possible (Ice > Thunder > Dark > Everything else)
Magic Skill Torques
Prism > Solitaire
Errant Slops/ Jet Seraweels for standard use. Although if you can afford Jet, just use that money to buy Mahatma Slops.
Penitent's Rope
Errant Houppelande
Qiqirn Sash +1 (Resting)
Beak Necklace +1 (Resting)
Arborist Nails (Resting)
Antivenom Earring (Resting)
Igqira Tiara (Enfeebling)
Igqira Lappas (Enfeebling)
I would say most of this is great, with a few modifications added to it.
As I know, currently the entire Yigit set is one of -thee- best HMP gearsets you can find. Not to mention it is free.
I do not have the information on me currently so I'll try to make an estimate.
Just be reminded, BLM is not a job like SMN, where you stack massive MP to compensate for your MP if you require/wish more MP on your overall character.
Thats why you invest in a HMP Gearset, to provide the fastest MP regeneration possible, when you're close, or completely out of MP(Should hopefully never happen.)
Here is a list of what I currently use. Provides you with a +26 HMP Gearset, not including the 1mp/tic Auto Refresh you obtain from the entire set, which converts to roughly +5~+6 HMP a tic(per 10 sec after the initial 20 tic starter which provides you no MP regen).
This is not including Melon Pie +1(+2? or 3? HMP), however I prefer Cream Puffs over Melon Pie, which is a straight +7INT over a +20~30MP and 2 HMP and 5 INT..I may be wrong on the stats.
Pluto's Staff +10
Yigit Gomleck +5
Yigit Turban +1
Yigit Gages +0
Yigit Seraweels +2
Yigit Crackows +0
Quqirin Sash +1 +3
Relaxing Earring +2
Insomnia Earring +1
Beak Necklace+1 +2
Jet Seraweels are the alternative choice for people who are biased against having -stats equipment, so if you wish +1INT more over no negitive -VIT(Main factor on Mahatma), then by all means do it. If you want to have the best, then Mahatma is the better alternative, and seems cheaper than Jet at times.
Of course Morrigains will beat any of these, with a whopping 10 MND and INT with MP and HP? Possibly -emnity as well, with no sacrifice to -stats at all.
I also figured, after you have capped 8/8 Elemental Magic merits, AF1+1 Wizard's Gloves, Elemental Torque is not really absolutly needed. Thats where you start making your high INT Build for HNM mobs, (330 skill? and X INT forgot it for the INT build on HNM), as to using Uggy Pendent/Philomath Stole/Prudence Torque during nuking which Uggy's latent don't activate. Even then, not really wise to use Uggy Pendent on HNM less your resist rates are close to floored(If that's possible).
Thats providing you have Elemental Skill Gear build: AF2 Helm(+10), Nashira Crackows(+5) AF1+1 Hands(+15 and +3 INT), Merciful Cape(+5), will most of the time get you consistant nukes on endgame HNM. Just be forwarned tho, stacking alot of Skill on mobs such as Fafnir will give you deminishing returns, however stuff like Khim where resists are alot higher, or Cerb, then this gear might or might not be pluasable. Otherwise you are cutting off possible dmg that you could add, when you have overflowing amounts of elemental skill.
You'd need to talk to Darthtaru, Pchan, Hmk, or a few others on these boards to get the best possible thing for these I would assume. Those some of the notable people on the boards that I'd be referred to via BLM questions that are more advanced. Darthtaru I have seen does consistant nukes on mobs such as Cerb or Khim with barely if not much at all resists.
I'd go into the elemental Debuff INT build, but you can wiki that, and its a very good alternative to BLMs of whom do not have a good nuking setup, but want to do some decent dmg while debuffing the mobs & retaining their other uses.
Can get good elemental skill gear, while stacking INT and have barely many resists on high lvl mobs and normal, just by having the simplist gear availible(sp) to you. This also makes room for error, as you may swap around, and not loose as much MP from a resist, and makes you one of the better /random stunners at camps. Just simple fast-casting debuffs, and retaining your ability to quickly stun if needed.
If you do not have all the possible rare/ex gear from Sea/Sky etc, simple AH bought gear can suffice, but will not always outperform the alternative, of course.
But like you've stated, you're most likely using it for casual gameplay or when its needed, so the basics would be best, if you're not going hardcore BLM, then ignore most things above this line.
The basic normal gear, HMP gearset, and Stun is all you really need otherwise as the casual BLM. I'd look into the elemental DoT setup and information stated on wiki, and there is a LJ somewhere about BLM and elemental Debuffs, and some good setups for certian mobs, while retaining the T4 Debuff(since its not mostly possible to reach the T5 Debuff -5HP tic without being Taru Naturally, thus possibly needing Kirin Pole. But this is considering the person lacks INT 5/5 Merits, and do not have Salvage gear availible to them)
Hope this helps, even tho not all of it related to your post!