I use this strategy to great effect:

1. Disband 1 or 2 units of your Thessalian cavalry and your navy.

2. Capture Athens and enslave/exterminate them. Their mines will put you back in the positives.

3. Usually at this time Pella has been besieged a few times by minor armies. That's okay, I can't remember a single time where they took it.

4. Take your army under Antigonos, reinforce it with most of your garrison from Corinth, and take Sparta. Enslave/exterminate.

5. You can then focus all of your attention of Epirus. To do this I head straight back to Pella and fight off whatever army is besieging it.

6. Wait a few turns, get some cash, retrain your units and recruit some new units. I usually recruit 2-3 phalanxes from Pella and a few Akonkistai from Demetrias. I never recruit those javelin horsemen, I just use family members for their bodyguard and whatever Thessalian cavalry I have left.

7. With this army you should be able to capture all of Epirus.

Hope this helps.