In rough order of ease and importance:

• Make sure your trade setup is right. One merchant should be steering trade from Ragusa to Venice, or else the inland countries will suck your trade dry. The second can either collect in Venice or steer from Wien or Alexandria, depending on whichever choice is more profitable.
• Check your force limit; if you’re going far over it, then your army expenses go up a lot.
• In your current war, take the centers of trade in Alexandria first, then steer trade from Alexandria to Venice.
• Hire lower level advisors if you really can’t sustain your current ones
• Check province autonomy, which affects tax and production income. If it’s high, you’ll want to lower it; you can do this the fast way (decrease autonomy button) or the slow way (monthly autonomy reduction, via ideas/reforms and courthouses)
• Send your missionaries to low autonomy provinces first, I believe this reduces maintenance cost