Start slow. There is no need to go on a conquering spree in your first games. Concentrate on education and economy. You can start warmongering in the late in the 1870ies when you are well-off otherwise.
Make sure to check whether your factories are making a profit. Early in the game they often don't. Shift your clerks and craftsmen to the factories who turn a profit, even if they're producing boring stuff like glass or fabric. Tax your rich class as little as possible (15% tops) and go easy on the tariffs to give your capitalists a chance to build you other factories.
Set your education spending to max and, if at all possible, your crime fighting, too. With moderate taxes for lower and middle class (50% tops) that should keep your pops reasonably happy. If you need more money, make sure you have enough soldier pops to give you some manpower and set defence spending to max. This allows you to set army maintenance very low and still have an army that can fight during the first week of any war. If you still need money, consider raising poor taxes (Belgium can also lower crime-fighting as they have few provinces).
If you're not playing VIP you might want to try colonizing early on, but with V:R the best spots will be probably be gone once you get the necessary goods and money. So you can just wait until the minimum life rating for colonization goes down (Medicine, Machine Guns, Nationalism & Imperialism are the needed techs) and go for the suboptimal spots.
Belgium: Don't fight much. Wait till the Treaty of London event fires. You'll probably get your independence guaranteed by UK and France. This will keep the Dutch off your back. Concentrate on Cultural, Commerical and Industrial techs until you turn a decent profit. Start putting more pops into factories once they turn a profit.
Brazil: Once Dom Pedro assumes rule things should start looking up. When playing VIP you'll manage to take care of the Piratini with the reinforced starting troops and another cavalry unit (with cuirassiers, if possible). Try to stay on the UK's good side and buy their provinces before you start any serious wars. You can grab Uruguay early on, but if you wait they'll probably attract more immigrants. Go slow with industrialisation and concentrate on industrial, commercial and cultural techs. Don't lower crime fighting below 50% for more than a couple of years.
