The fact that you have to understand is that sometimes you will lose in the game. So, you will need money in your bankroll to continue playing and good strategy. To make your money stay longer at your account and multilpy, you need to learn some rules.
The house advantage in blackjack is 0.5% especially when you apply the basic blackjack strategy. A typical example of blackjack games with such a house advantage is blackjack with multiple card decks.