If you can I would suggest working your way up for the Lightstream/Trailblazer weapons as well. Technically "all" of the weapons are obtainable in-game and the only things you are missing are the Erebus stones (I cannot recall what they were officially translated as) but that should be obtainable and farmable later this week.
The parts you will need are the following:
- Profound Weapon+35 (this specifically has to be the weapon you want)
- Any Detonation Weapon+35
- Any Cladium Weapon+35
- Any Allure Weapon+35
- Any Xerraire Weapon+35
Putting those five together will give you the Celestial/Starquake weapon after you get its needed materials and using the extremely rare stone, Founder's Amphirite (current Mission Pass Tier 30 reward or a title reward), you can get the Lightstream/Trailblazer weapons.
If you already have Atlas EX I recommend getting these as well because these are just as rare and are sidegrades/utilities to one another. If you decide you do not like a class or its weapon type you can always use the Category Change function to swap weapon types down the line due to how rare these weapons are.
If you otherwise have something else you want to grind for and are not burdened by the time or effort needed, I would recommend looking into the Ophistia and Novel series of weapons as well. Ophistia is among the lowest-tier fifteen star weapons due to how accessible they are (Nemesis, Raven, Invade, and Ares each at +35 and combined with 400 Excubes) and have situational gains in power where they can become stronger than Atlas EX and Lighstream if you play into their mechanics (having multiple Mags with specific photon blast creatures). However, if you pick up Novel weapons they will later upgrade to "Liberate" weapons which feature the first use of an S5 S-Class Special Ability/S-Grade Augment which can be a huge game-changer if you are fond of the special fourteen star weapons such as Dual Bird, Lavis Cannon, Spread Needle, Gilhess Weihen, Gear Experience, Radius Arka, and more. These will be an upgrade to rival the Atlas EX and Lightstream series of weapons in Episode 6 and will definitely help you pave your way to the next tiers of weapons.
If you are not willing to invest too much for that just yet, you have a number of weapons you can stick to and rely on for the time being such as the following:
- Nemesis/Raven/Invade/Ares: These should still be decently usable but you are likely going to want to look for replacements because these weapons have already been showing their age especially with Ophistia in the picture.
- Ivlida/Supernatural/Jutus/Val: You are likely going to have these to upgrade to Atlas and Lumiere and later to Atlas EX so if this is still on the table for you then you should not have many issues running with these until then.
- Profound/Detonation/Claudium/Allure/Xerraire: Similarly to above, if you are going to create the Celestial/Lighstream weapons then you will be wanting to hold onto these so you may be using them until then.
- Special Fourteen-Star Weapons: If you have a hold of these and their Plus Potentials and you really like their mechanics you can definitely hold onto these until you get your hands on a Liberate weapon where you will be able to inherit most of these potentials in some form and use them on stronger and future weapons that are compatible with S5 abilities.
- Occuld Weapons: If nothing else I would simplify these as the "new" Sigma weapons. You should no longer be using Sigma weapons at this point when you have these available.
