The first thing is don't go in thinking you're gonna double your money in three months, because that's how people lose everything. With 500,000 pesos you've got a decent cushion to start with, but you need to understand that the stock market goes up and down, and if you invest money you're gonna need in the next few years, you're gonna have a bad time when a crash comes. Before you touch any app, learn the basics: what an ETF is (funds that invest in several companies at once, way safer than individual stocks), what your investment horizon is (how long can you leave the money untouched?), and what your risk tolerance is.
Apps like Fintual or Nubank are good to start with because they have low fees and let you invest with small amounts, but read carefully exactly what commission they charge and how they work before you put anything in. A good initial strategy is to put the money in bit by bit instead of all at once, that way you avoid the bad luck of putting everything in just before a big crash.