Lugoae, like most Levy troops in EB, are quite effective for their Price. Cerainly one of the cheapest Units, almost as good for garrisons as levy skirmishers. Not quite as ferocious as their Germanic counterpiece, certainly more usefull than Hellenic Native spearmen.
They cerainly have their uses, for one they are great to depopulate unruly cities, as they don't Need fancy barracks. furthermore they are a cheap way to outnumber you enemy, as Long as you have Regulars to actually hold the line/do damage they can fool the enemy into fleeing.
Another use is to Screen your ranged troops, bog down cavalry or take enemy fire. On loose Formation they can seriously complicate a cavalry Charge(and do some actual damage) and due to large shields suck up a lot of precious arrows and bullets.

Unless I'm in REALLY big Trouble, I would avoid having more than 5 Units in an army, two are more ideal. When used as meatshield frontline troops 3 or more Units of them become a liability to army morale.