These are what I consider staple and carry with me everywhere:
Staple
Charge Vulcan 50h
Charge Arms 50h
Frozen Shooter 10h
Heaven Striker
CV can be replaced by berserk/spirit counterparts or Vise or TypeME/Mechgun with charge (event item) if the situation allows it and if you prefer them.
10h on FS is sufficient for RAmarl to perfectly freeze Ill Gill on the second attack; you'll generally tek it right and get 15h+ of course. If you plan to share it with another character, you might want more hit.
Heaven Striker can have hit (very expensive) or be hitless. For hitless ones I like having high %s in Native, Machine, and Dark. Hitless ones can actually be glitched like slicers can, and if you get used to it, it can go a long way. Hit ones just allows you to attack up close or be lazy (which is good in its own right).
The following are what I have in my sideboard and take them out for certain areas (still minimalistic).
Sideboard
ES Shot with Hell special
ES Needle with Hell special
ES Needle with Demon's special
ES Mechgun with Demon's special
Arrest/Hell/Demon's Raygun 50h
Arrest/Hell/Demon's Laser 50h
As you can see, they're ES Weapons (a.k.a. S-Rank Weapons) and nonrare weapons. For a minimalist RAmarl, once you have the staple items, the biggest improvement are now the S-Ranks, especially Hell multi-target S-Ranks. In case you feel S-Ranks are too expensive, then prioritize getting the important ones. While Hell ES Shot is slower than Hell ES Needle, the range allows you to cover a much larger area without having to move around a lot. I tend to use these more when playing with a group, and Hell ES Needle more when soloing.
While Demon's is a strong special, Demon's ES weapons are less efficient than Charge nonrare weapons on weak targets, E1 grunts and the likes, since Demon's activation is probabilistic and highly varied. They are however very effective on high HP targets. Since RAmarl has the lowest ATP out of all Hunters and Rangers, there are certainly some scenarios where Demon's is more effective, for example, when RAmarl couldn't kill a target in two charge vulcan combos. In this case, Demon's ES Mechgun will perform better. Similarly, there are cutting points for Demon's Needle/Shot and Charge Arms, but with so many targets the results are very highly varied, which makes them less reliable as is, and it would be required to use HS or similar weapons to clean up afterward. Shot was not listed because from my personal experience with Demon's ES Needle, I felt I needed multiple combos for it to be reliable. (Take this with a grain of salt as I haven't actually used a Demon's ES Shot before.) It is for sure useful against multiple high HP targets, for example certain waves in Raid on Central Tower consists entirely of mini-bosses.
About nonrare weapons, I actually prefer Rayguns over Lasers in many cases since they're faster, and has a shorter glitching distance as far as I can tell. Lasers are mostly important for attacking at rifle range, for when you need to snipe dangerous targets (Meris), or when targets spawned far away. Some people would suggest Bringer's Rifle or Holy Ray, but they aren't much of an improvement since it's the special that's important, and those two are rather expensive. I find their nonrare counterparts to be fairly sufficient.
Note that Arrest Raygun/Laser is only used on Dorphon/Girtablulu.
Now, some of the more situational items.
Situational
Cannon Rouge
Excalibur/Tyrell's Parasol/ES Scythe with Hell special
Vivienne/Girasole
ES Needle with Arrest special
It's hard to make a cutting point as Hell/Demon's can still be considered situational, but the weapons listed here are generally more niche as they are less widely applicable.
Cannon Rouge is the cheapest boss killer around. By "boss killers", I'm referring to weapons that can do decent damage on bosses when they're not targetable by regular weapons, such as when they're flying or swimming. Berserk ES Launcher is another option, and these two weapons are better for different bosses, but I want to keep my list here minimal. Cannon Rouge is also one of the most important dubswitch killers, alongside Dark Meteor (very niche) and some other weapons.
Excalibur/Tyrell's Parasol/ES Scythe with Hell special are what RAmarl can use against a group of lizards. Excalibur is strong and fairly fast but only targets up to three lizards, and requires the lizards to be really close to each other. Tyrell's Parasol is her strongest damage-based partisan, and it would be more effective for slightly more scattered and larger group of lizards, but it requires decent hit to be useful. Excalibur and Tyrell's Parasol can also be used on other enemies, if the enemy grouped up nicely. ES Scythe with Hell can sometimes work wonders and clear off a whole wave of lizards at once, but it's less effective against desert lizards.
S-Beat's Blade is probably worth mentioning while we're on the topic of lizards. I don't have personal experience with it, but with Hell and hit, it can potentially kill multiple lizards in one combo. It is probably less effective against desert lizards though, just like ES Scythe.
Against single lizards, you might be able to kill in one combo with a sphered Excalibur (I'm not sure), but if not, then Vivienne or Girasole can be used to take down lone lizards. For most other enemies, Charge Vulcan/Demon's ES Mechgun will generally be enough as a RAmarl, especially if the target is frozen first. Girasole also has a niche use of intentionally reducing your HP, which can be used to proc for mag invincibility by taking certain fixed-damage hits.
ES Needle with Arrest serves one main goal: to arrest a group of Dorphons. On android classes, they can get away with hit Spread Needles since they have an innate boost to paralysis specials, but on RAmar/RAmarl the success rate of Spread Needle is too low, hence they should only use Arrest ES Needle. This weapon is also good for soloing as it's decent for crowd control. That's about it however, and apart from dorphon spam quests it doesn't get a lot of use in a party.
For frames, it does not matter too much. The only offensive-oriented frames she get are Sweetheart and Stealth Suit. You can also use defensive armors, such as Brightness Circle (my preference when it comes to defensive armor since it has comparatively high EDK). Lieutenant Mantle is good, but you might not want to use it if there's a cast around as you might blow their traps up at the wrong time.
For barriers, as mentioned already: Ranger Wall, then Red Ring. You can also get an Anti-Dark Ring in your sideboard.
For units, I personally just use V101/V502 and keep the other two slots empty usually. Occasionally I would use Cure units in those slots. PB/Increase might be a good option too, when doing long quests and you find you're generating PB too slowly.
That's it for now, you'll gradually learn about other fancy/niche weapons as you play and read what other people say. However, I think I could comment on Baranz Launcher and Snow Queen a bit more. Baranz Launchers are partial replacements for Charge Arms, with less targets (4 vs 5) and higher ATP. Its bullets are slow, which makes it less effective against fast moving enemies. Due to this reason, it's mostly used on slow-moving or frozen enemies. The main use for this weapon is to have it sphered, at which point it will kill certain enemies faster than what's possible with Charge Arms, sometimes killing a group of enemies with one combo. A sphered Baranz Launcher is a very late game item.
Snow Queen is not a replacement for Frozen Shooter, since it cannot freeze high EVP targets reliably. It is good for freezing targets that are behind other enemies, or just general crowd control in a party. It's more effective in a party than solo, due to monster desync. However, it is usually not possible to freeze targets in later areas reliably with Snow Queen due to insufficient ATA, which makes it less concise than Freeze Traps.
