
Originally Posted by
Dulce_et_Decorum_Est
The Romans like nothing more than crushing things under their hob-nailed boots. Respecting the dignity of other human beings is for sissies like Marcus Tullius Cicero, which is why they nailed him to the rostrum.
To beat the Romans, you have to be colder and more calculating than they are. You have to replace your heart with an icicle. You have to enjoy stomping on flowers and making puppies cry. You have to be as heartless and amoral as Genghis Khan, or maybe even Batman.
All this, of course, is significantly expedited by the stupid AI.
Hit the Romans where they're weak in battle. If they're still Pre-Marius, the Numidians still have better archers than they do. Post Marius, well, then they have pretty good archers, but yours are still arguably more cost-efficient.
Pre-Marius, the Romans have awful cavalry. Numidian cavalry can nearly beat equites hand to hand, that's how bad they are. Silly Romans, horses are for nomads! If you let your numidian cavalry skirmish with the equites before fighting hand to hand, they're trounce them every time.
Actually, it's worth noting that Numidian cavalry are one of the finest units the Numidians have, and one of the finest early missile cavalry units around period. They're one of three units in vanilla on a light horse with the hardy attribute (the other two are Arab cavalry and Scythian horse archers), meaning they're faster than anything you'll ever fight. I mean, if you take it all the way to the Scythian border playing as Numidia, you don't need my advice.
That being the case, it's trivially easy to run them behind the pre-marian units and peg them with javelins while your foot skirmishing elements keep them facing the other direction. Half of hastati resistance to projectile weapons comes from their shields, so if you get behind them you should be able to thin them effectively, even with Numidian cavalry. If the Roman general or equites come out to play with your jav-cav, so much the better. Lead them on a merry chase away from the rest of the battle and watch gleefully as your skillful horsemen attrition them down to nothing and then slaughter them with little pocket knives because they have higher endurance and morale.
Since one of the strengths of the Roman infantry is their morale, you should do everything in your power to make it lower. Aside from flanking them and bombarding them in the initial stages of the battle, which you should be doing anyway, you have a useful tool at your disposal for removing enemy generals from the field.
Take a good hard look at Numidian camel riders. They're basically long shield cavalry with a huge bonus against anything on a horse. Aside from being capable cavalry all around, they are general killers par excellence. As Numidia you are blessed; you are one of only three factions to get a camel unit in its roster. Egypt gets goofy and useless camel archers, while Parthia gets camelphracts which are too slow to reliably hunt down command elements and too expensive for those desert bumpkins to field in numbers anyhow.
Take one unit of numidian cavalry and two of camels and bait the general out before slamming him with camels, or any variation on that, and make sure that those pompous guys in the expensive armor aren't around to inspire the enemy troops.
Strategically, make sure to grab all of Iberia. It's worth quite a bit of money and regularly mints high-quality mercenaries, both of which you'll need to maintain numerical superiority over post-marian Romans. Is numerical superiority necessary? Not if you're a really slick commander, but it sure is handy for the rest of us.
Forget throwing your imitation legions at the Romans. First, as you identified, they take too long to build. By the time you have a serious number of them, the Romans will have over-run Gaul and will have too much money. Second, their legions are better than your knock-offs. Sorry, you can't beat the originals I suppose. Stat-wise Numidian legionaires match principes. The legionaires proper with the historically inaccurate plate armor that the Romans will be minting? Those are 50% more expensive, but they have more than twice the morale, substantially better defense and somewhat better attack stats as well. In short, your fake-legions will break themselves on the real thing.
Save your Numidian legions for efficiently killing those time-traveling Egyptian anachronisms. Their hordes of cheap infantry will be much less bothersome against disciplined troops, even if they are a shoddy imitation of someone else's.
This brings me to point 2 of the grand overall strategy; KILL EGYPT!
Not only is Egypt overly smug, possessed of annoying diplomacy messages and a squirt of lemon to the eye of history, but they've also planted their fat bodies on top of some of the must lucrative real estate on the southern half of the game's map. I highly recommend killing them and taking all their stuff. If you deal with them early, your troop types will counter theirs handily. They like chariots? Fine, you have lots of skirmishers. They like big, inflexible phalanxes? Fine, you have lots of fast units that get bonuses in the desert.
Hope this helps, and happy gaming.