Brazil has one of the largest and most relentlessly aggressive solo queues in the game. Nobody plays for scaling, every lane is a fight, and a passive early game is punished immediately. Whether that is a feature or a problem depends entirely on what you want out of a smurf — for mechanical practice under pressure it is excellent, for learning patience it is the worst shard you could pick.
It is also cheap and always in stock. BR sits with the LATAM shards at the bottom of the price board, which makes it the obvious choice for a throwaway account you intend to play loosely. If you want the essence to go with it, Blue Essence Rich on BR is one of the better value combinations on the entire site.