Anytime you put money into anything with a chance of losing it or gaining more it’s a gamble. If it pays off it was a worthwhile investment.
When you invest in a company you are betting on an outcome that you expect that investment will grow based on your own, hopefully informed, predictions. When you place a wager you are betting hoping for a greater return on that wager based on your own, again hopefully informed, predictions. Yes some gambling is entirely random like the lottery but most such as sports wagers, card games, etc need just as much knowledge and skill to be successful as playing the markets does. Any investment is a gamble because you can never fully know the outcome.
But with regards to Robinhood I would say right now that gamble is probably too big imo. Unless you got in early when it was very cheap and are still sitting on a profit it would be a big risk to expect it to make any big upturns in the short-medium term and there simply isn’t enough data to predict long term potential at this point.