Sealed sword line is not bad...

Every sword user should have a Leviathan and a Divine Avenger in their arsenal.

Skip the cutter and the troika lines. Cutters are terrible after T2 and Leviathan is better as a normal sword.

Final Flourish or Barbarous Thorn Blade are both viable options if you want a piercing sword.

Gran Faust or Acheron for a shadow sword.

The Elemental Brandishes (Glacius, Combuster, Voltedge) aren't bad but I prefer DA because of its knockback and its better charge.

I'd say you need a minimum of 3 good swords.

The calibur is a given. If you're not sure what you need for an upcoming Stratum, the Calibur line will generally fill any holes or blind spots you might have in your loadout. I have one, and I don't use it all that often anymore now that I have a good selection of other weaponry, but I've been more than glad to have it on several occasions.

I'd also seriously recommend having either a Snarble Barb or a Flourish on hand. Either will make dealing with fiends and beasts a breeze, and being able to quickly kill Devilites, Greavers and Alpha Wolvers is a good thing.

After that, it's a choice between the Sealed Sword lines, or the Brandish lines. You'll want at least an elemental damage sword, if not a shadow damage one as well, and both lines provide both benefits. Elemental Brandishes come with the potential for Status ailments on their charge attacks, but in most other respects they're similar to the Calibur. Sealed Swords just hit hard, being heavy-type swords, and the Faust can potentially inflict Curse which is a stupidly good status effect. I'll just go on record here as saying that it doesn't happen all that often though.

As for guns. If you want something that's good for dealing with Constructs and Undead, then obviously you want something Elemental. If you want an Elemental gun at all, then you want a Pulsar. The 2* is normal damage, but there are 2 upgrade paths and the one that leads to the Polaris is Elemental damage with a chance of inflicting shock. At long range the shots also explode in a pretty wide area and cause pretty strong knockback.

Failing that, you can't go too far wrong with any of the Alchemer lines. Firotech is probably the best one for damage, but the status can't co-exist with freeze. Cryotech can potentially stop enemies in their tracks for a while, but the status can't co-exist with Fire. Voltech is a good middle-ground, and its status doesn't conflict with anything.

If you're planning to go solo often, then the Catalyzer lines are also very good options. They suck terribly in most groups though, as the slot shot speed and the charge-shot mechanic don't work well with other people interfering and pushing mobs around.

I actually really like the Troika and its upgrades. I'll eventually be upgrading to the 5* one at some point, but I do have to tell you that its charge attack is next to useless in general play. It's also very slow, especially the second swing. The Sealed Swords are faster, have more useful charge attacks (especially the DA), and can exploit damage weaknesses.

Oddly enough though, while the first swing of a Troika line sword outdamages the equivalent Sealed Sword on a neutral target, the second swing doesn't. Which I find strange. You get few opportunities for using the second swing on a Sealed Sword derivative without getting you face smashed in, and fewer still with the Troikas, so this strikes me as a little unfair. The Sealed Swords also have the same range, even though the Troikas appear much larger.

Troikas do have pretty obscene knockback. As I said, I really do like them, but I can't in good conscience actually recommend them to anyone until OOO does something with their damage and charge attack.