Offensive of Coalition (Briton campaign)

Forgot about that campaign, but I'll have to say the ai moves pretty randomly, although you can probably manipulate some of their movements consistently. Archers are easily killed off by a bunch of infantry units and a cavalry gen(preferably heavy cavalry so they can take some hits). 

I did this with cavalry Commander, Pompey, Drusus, Pacorus I and Crassus.

Pompey and Commander are deployed on the northern force.
The rest on the southern force.
Then, destroy the military camp in the northern city and replace it with a market.
Remember to use this market to maximise coin output.



The northern force will march towards the archer gen, defeat him and take his city.
Then, march southward and take the lvl 3 city.

Upgrade the city to lvl 4, but don't build anything.
Convert the stables to an archery so that you can spam slingers to defeat the inf target gen.
By now, your reinforcements should arrive.
The Woad Raider and Heavy cav should cross the river and link up at this captured city on the Roman's coast.

Lastly, march southward and take the last city. From here, spam light inf to attack Caesar.



The southern forces will march southward.
Reinforce them every turn with 1 scout unit.

Ignore Mandubracius, attack the military camp and flank the city centre from both sides.
Use Military Tactics to weaken the city and/or the nearby enemy.

Taking the city spawns player reinforcements.
Send the archer to the Celtic traitors' camp.
Upgrade the city and build a market on the empty tile on the east. This gives you more coin output, but don't spend money to get the Cultural output feature.

Build 1 double stacked inf every turn and slowly push eastward. Use Spy and Plague to weaken the enemy.

Do NOT take the city or allow an ally to walk into the empty city before Caesar is defeated.
Stop building troops in the eastern most cities if you still have not achieved the economic secondary target yet.