Through practice, one could learn experientially about a game's variance, the impact of betting on different numbers of spots, and the impact of varying or matching your bets / patterns across multiple cards in multi-card games. This can be important when it comes to expectations and bankroll management. You would also learn the mechanics and features of the various games to decide which one is most enjoyable to you.
The game is random, so it would be a mistake to think you'd learn any secrets to winning or patterns that are "luckier" than others. But for the reasons above, you might be a "better" or more happy player having practiced for free before playing with real money.