A lot of people gave you some general purpose tips and tricks. What with the main conceit of Victoria 3 being 'you want to deficit spend slightly, borrowing from your population and raising taxes as much as they can take so that you can build the future'. What I'd like to mention are some Brazil specific things since that's who you played.

Brazil starts as a slaver country with a good amount of arable land, a small population and terrible infrastructure. As always, you want to identify the state traits that give your people and country an advantage.

Brazil has good state traits for Iron and Wood production in the North, and plantation goods along the coast. The north is dominated by the Amazon Rainforest, however, which lowers construction efficiency. What this means is that it takes longer and therefore costs more money over time to develop the north. Which you'll want to avoid doing until Rubber comes into play. That will let you change the Amazon trait into something that isn't nearly as crippling.

Brazil's North and South-eastern coast is dominated by states that are good at producing sugar but have bad infrastructure, either from legacy industries, plantations or low population. Very few Brazilian states have inherently good infrastructure from river systems, which leaves São Paulo and the Southern States as your initial frontier for development.

São Paulo is good for coffeeculture and the South is good for agriculture in general, while also having some paltry but at least existent supplies of Coal. Minas Gerais, your central state, has some Gold and Iron. Brazil is poor in mineral resources in general. As a result, the question you have to answer in the early game is: do you focus on an industrial revolution or the plantation economy? Plantations, at least to start with, don't require inputs other than labour. But on the other hand, Brazil does have flavoured companies that focus on Wood+Paper (Kablin) and Coal+Iron+Steel (Ipanema).

This question is less of a no-brainer than it seems. Agricultural and Wood development is cheap and takes a short amount of time to set up. Mines and factories are expensive due to the amount of time it takes to get them running. Brazil's relatively small population means that focusing on resource exports of Wood, Coffee and Sugar is a valid strategy.

Your early game priority is to either liberalize Citizenship Laws (attain Cultural Exclusion) and/or enact Open Borders. This is because under Migration Controls foreign pops will only move into your country if they have a (sans Religion) acceptance of 60. Cultural Exclusion gives you access to European migrants. Multiculturalism will eventually give you access to all of the world's migrants.

I won't spoil the Journal entries. Just know that if you succeed in preserving the Monarchy you'll get a ruler that has a pro-Multiculturalism ideology in the form of Empress Isabel. Just don't sweat about it. The most most important entry is about the Brazilian Nation, which turns the regional cultures into Brazilian. If you complete that but goes Republican or even Communist, then its hardly a failed run.