You can actually buy Bitcoin fractions on pretty much all the major Brazilian exchanges like Coinbase, Kraken, or even through your bank's app, so you don't need much cash to get started.
The thing is to start small, investing only what you're willing to lose, because crypto is super volatile - I've seen people who got in thinking they'd get rich in a month and got totally wrecked. My advice would be to open an account with a well-established exchange, make some small purchases to get the hang of it, and only increase the amount as you better understand how this crazy market works.