Eeh. Don't split your income, I always find it very ineffective. Always go 100% for something. Either 100% of income to technology, or stability, or mint it. Fully. Now, 12 months of minting without governors = 1%, with governors in every province = 0.75%. Just a short reference
Don't bother with negative monthly income, it's really better after all than inflation and it leads you somewhere around...nowhere. First decades are always tough, just invest in bailiffs (take loan if you need to, you'll repay it easier after having new baillifs). Now, the only situation when you should be bothered with negative income is when you have army over your support limit - then you're paying much more AND you'll be automatically taking loans once you hit 0 ducats. But in general at some point during peacetime you'll find out that you can easily keep up with just yearly tax added to your treasury every year
Negative income ain't bad, really. At some point you won't even notice it.
When we're at minting - massive five-six years full mints are encouraged when you are hitting level of any tech allowing you to create manufactories. Certainly a good option is to rush 3rd infra a bit and gather money for a few refineries. Don't mint when your monthly income is low! Manufactories are mostly 16th Century thing when you are around 80 to 100 ducats monthly. Then you can mint for five-six years and spend it all on refineries. Massively speeds up trade tech research - allows monopolies - makes trade useful - you can become a true millionaire. Well, that was long one. To sum up...
1.) You can easily make it with yearly income, mint only when you have loans to repay or when you're at superiore emergency situazione (but you'll probably take loan and repay it later rather than mint). Spend your money wisely, especially during early phase of the game. Always keep some reserve cash.
2.) Baillifs, baillifs, bailiffs. First thing I'm doing after acquisition of new province is BAILIFF. NO QUESTIONS. Unless you don't have money, wait until January then. AND THEN BAILIFF. NO QUESTIONS.
3.) A huge mints once you can build some manufactories and have a plan for that. I remember my epic struggle to get 4 refineries going in my Georgia's game on MyMap. But I succeeded and Georgia turned into regional power. You don't have to rush 3rd infra (some countries should have other priorities), but for Western Powers it is certainly a good thing to enter 16th Century with a few refineries.
4.) Once you have governors, you can really mint whenever you want, inflation will be eradicated anyway, at rate 0.25% / year. If you are really a major power, pull some more 5-6 year minting actions and build more manufactories. Manufactories are good.
5.) Trade, trade like crazy after you've hit 3 or 4 trade level. Get access to Asian CoTs (map exchangement/raiding of enemies capitals), make sure your traders will make it to 5th place in CoT and leave them there. At this point your income will skyrocket soon.
So, it turned into little Anjin Miura's Treaty on For the Glory Economics. Hopefully it will be of some use
Certainly it's not the only way to be successful.