The method described below has been tested with every major country available in the vanilla game plus some modded in. The game version tested was the full version with all DLC's. This guide only describes the fastest method of getting rid of the debt, getting into surplus budget and building up the reserves.

Be advised that this method is cheesy and will strip the game of any challenge even before the first election!

You have been warned.

1. Set income tax at 55%
   
2. Invest into education
   
3. Profit!
   
   
   Longer version:
   
   
   1. Income tax
      You need 30 political capital to raise the income taxes, so it is unlikely you will be able to do it on the first turn. Check how much political capital you get each turn from your ministers and plan accordingly. Decide what you want to do in a long run and pass acts that will help you, but be careful to only spend as much points as you need to have at least 30 next turn. Once you have at least 30 on the second turn, immediately raise taxes. I found out 55% to be a good number. Middle class will hate you the most, but you can remedy it later by passing other acts. Right now you are interested in getting rid of debt as fast as possible and having enough surplus to sponsor other things to progress your country. With that one raise you should have enough money to not even need to cut funding in other areas, like pensions, state housing, etc.
      
      
   2. Education
      With the surplus secured invest heavily into education. Raise state school funding to maximum, introduce Adult Education Subsides and Technology Colleges.
      Once those kick in, a newly educated population will reduce unemployment, poverty and increase technology level, productivity and thus increase GDP. Higher GDP means more money from taxes.
      
      
   3. Protfit!
      You should be able to get rid of debt in under 2 years, depending on your chosen country and difficulty level. Now start appeasing the populace. Wanna go communist? Wanna go capitalist? Wanna go for the theocracy? You are free to do what you want now, as you will be swimming in cash.
   
   That's it. Good luck surviving assasination attampts.