Some good tips for you:
Try to get your education, health, and transport index to around 150.
Try to keep employment above 90%. Do this by building corporations. Try to focus on profitable corporations. Services are usually a safe bet.
If you don't already have a CEO, create a CEO account and build corporations in your own countries to start.
I would keep corporate tax around 20-30% too.
Get rid of all military spending on your secured country. It is not necessary, and most of the military units are useless. When you are ready to conquer another country to expand, you should purchase the select units that you need.
Set social security payment to 80%.
Set country ordering quality to max to increase welfare index. Having a higher welfare index allows corporations to produce more products, which means more profits.
For corporate settings, set salary for state corps to 200 and for CEO corps to 300-350. Set order supply quality to 210, and set purchase and sale strategies to best. Make sure corporate upgrades are set to automatic for existing and new corporations.
Close down your crappy unprofitable corporations (anything in massive surplus, and any defence/offence industries).
Set your education priority settings to: 5, 5, 6, 7, 7, 5, 5, 10, 10, 20, 20, 20.
Those are just some random assorted tips that I use in all of my countries. I play on LU btw, feel free to contact me anytime if you need anything.