I recomend you use only high taxation if you have govenors in those cities, with high your govenors wil get the best virtues. If youre losing money it means you have to large armies so use what you have to fight your enemies and be more careful of what you build, try not to have to many castles and only militias to defend cities and the good troops to fight wars. You should not need to have bigger armies to beat the AI though if youre using auto calc when fighting battles its understable but try to fight them your self usualy works best early on.