Honestly...I'm going to have to disagree with points both of you (Somnia and Bear) have made. Bear with me, as this'll be long.
The main reason behind why I say the things I say is actually because of the existence of the Weapon Shop. You know, the one right by the Tekker? It will provide 90% of your basic arsenal as a Force, or should.
Force Weapons are bad because the main stat they boost is ATP. They give minor boosts to DFP, EVP or MST depending on class, but if you look at the numbers, they're basically gimped melee weapons with minor secondary stat boosts. Problem is, the ATP they give is kinda useless because it's a low amount (compared to "real" melee weapons) and they have awkward attack combos. On short-ranged weapons that put you in harm's way, no less.
The non-rare Force weapons are buyable from the shop for any ID. It may take a bit, but it's possible. That takes care of your easily-available DFP and MST boosts. EVP boosts are useless in Ultimate on any class that's not Hucaseal or Ramarl, and you're going to spend more than 90% of your character's total lifespan in Ultimate. That leaves the 9* Wands and the 9* Canes...but the 9* Canes are easily replacable by Summit Moon. The Magic Rock Moola that most IDs find is the only "rare" thing you need to make one of those.
The second problem with Force weapons is that you only ever really need one. The only variable boosts on weapons are the "percentages", Native/A.Beast/Machine/Dark and Hit. All of those only affect either a weapon's ATP or ATA. The main reason people "hunt" better versions of weapons they already have is to find a higher-% one, generally with the coveted "Hit %".
This is why I suggest Yellowboze, Purplenum, Redria or Whitill for Forces, in roughly that order. Yellowboze is a good all-rounder ID that has a slightly higher chance of finding hit% on weapons in Ultimate Ep2. Purplenum's "common" weapon drop type is mechguns. The more that drop, the better your chances of finding one with Hit %. Redria gets God/Battle, and if you don't have one, you'll want one. Besides that, it finds a lot of Slicers, and can get some good rare units (Cure/Shock, Cure/Freeze, God/Arm, etc). Whitill's probably the worst of the lot, but it has the easiest Cure/Freeze, and you'll trip over rare Slicers.
You'll notice that Yellowboze and Purplenum, between them, have most of Pinkal's "good" drops, as well as access to its rare FO weapon drops. Sure, the hunt may be slightly harder, but you only ever need one Fire Scepter. Purplenum also has the "most practical" Psycho Wand hunt, though anyone seriously expecting to get a Psycho Wand probably needs to have their head examined.
So Yellowboze/Purplenum take care of Pinkal's drops. But what about the weapons you need to do physical damage? And how can the lowest-ATA class in the game (Fomar) ever hit anything in Ultimate?
Simple. Hit %.
Hit % = ATA. ATA is disproportionately important in Ultimate, because enemy EVP skyrockets. Luckily for you, weapons are buyable from the shop with randomly-generated percentages. This can be on any weapon type, with any % from 0-50%. This includes Hit %.
This factor is how you're going to be able to equip a Fomar or Fomarl to use weapons for ATP-based damage. The fact that you can also buy weapons with Charge from the shop only makes this better. Charge uses meseta to deal extra damage. As a Force, you won't have the ATA to spam it, but it makes a nice finish to a combo.
Also, Fomarl has the second-lowest ATA in the game, at maximum. She only beats Fomar. However, despite the Newman Forces' much higher maximums, they have horrid growth. Fomar/marl can max their ATA early on with a good Dex mag. Fonewm/newearl need about level 170 or 180 to max both ATA and ATP.
What weapon types are good, though? I suggest Slicers and Mechguns. Slicers for multiple-enemy groups, and Mechguns for single enemies. By the time you're in Ultimate, the shop will be carrying at least some weapons with hit % and Charge. It may not be the yellow-tier (Vulcan, Diska, etc)...but you can find purple-tier or red-tier ones there. Mechgun and Slicer's base stats, as a class of nonrare weapons, kinda suck. You don't want them for their base stats, so the specific tier is irrelevant. You just want Hit % and Charge.
Ignore rare weapons. Most of the ones FOs can equip are utterly worthless, either because they're strictly melee range (which you don't want with your HP/DFP) or because you can't easily find Hit % on them. A FO with non-rare weapons with 50% hit, even without Charge (as Charge is ridiculously, brokenly overpowered) will outdo a FO that has stuff like Psycho Wand.
But with FO's relatively low base ATP and relatively low base ATP on your weapons, how are you to deal damage, you ask?
Whore out the variety of multipliers ATP-based weapons can get compared to techniques.
-Base ATP boosted by material usage and a Power/Dex mag
Fomar and Fomarl are both capable of using all of those. And with their high material limit, if you have the resources, you can jack their abilities up much higher than what their level would suggest. Fomar/Fomarl can (if you have the mats and build their mag correctly), max their ATP/ATA/LCK by between level 145 and 150.
For reference, max ATP/ATA/LCK on a Fomar lets you kill 80% of the enemies in the game in one mechgun combo, without using Charge. The only things that will survive a single combo are bosses and higher-tier single enemies (Bringers, Del-Ds, Belras, Sinows, etc). That's online, by the way. Without PB combo Shifta. Offline, few things will survive.
And to add insult to injury for the Pinkal casters...a Force built like this, without any permanent resources put into Mind, can still equip a Mind mag (without using any Mind Mats) and blow through Normal-Very Hard, doing maybe 30-50 less damage per cast than a FO that boosted their MST way up with Mind mats. That's the inherent imbalance of the system, but it's one that you can use to your advantage.
Just ditch the Mind mag for a Pow/Dex one (I like 5/115/80/0, which allows you to easily get Sato or Nidra, depending on your available IDs) when you start running into stuff that has several thousand HP and only takes a few hundred damage from even a "boosted" casting.
I wouldn't suggest trying to build a Force like this as your first character, but it's doable. It's just far easier when you can feed them the mats collected from another character.
The basic philosophy behind the whole concept is this:
Forces' basic stats before modfication (mags/mats) are keyed to them being "casters". However, they have a wide range of difference between their "base" and "max" stats. The stats that get the most benefit from having limited resources poured into them are ATA, ATP and LCK (as they benefit from the modifiers listed above). If you let your "base" growth cover the thing you're already built to do (and the thing that gains a miniscule benefit from pumping resources into it, Casting), you can do that adequately. If you put your limited resources into the thing that gets the best benefit, you gain another dimension to your character.
The difference between a max MST caster with all applicable tech boosts and one with no boosts at all is about 50-200 points per cast, depending on the enemy. That seems significant if you multiply it by the number of enemies you face...until you realize that most Ultimate enemies have HP in the thousands, and few of them come in large-enough, elementally-homogenous enough groups to enable you to get max damage per cast. You end up chipping away at the Fire-weak ones (except in Mines <_<), then having to finish off the few Ice or Lightning-weak stragglers that are still trying to kill you.
The difference between a max ATA/ATP/LCK character (which costs about as much as boosting MST to max) and a character with no ATA/ATP/LCK boosts is around 1000 points per combo, if not more. Especially with mechguns (and their flinching/pushback), you gain an element of battlefield control. With a God/Battle, you can keep stuff pushed out of your face til it dies, without having to move around.
Try doing that with Foie on something big.