Actually gambling depends on your luck and as a base you cannot replace any strategy here.
There are skill based gambling where your winnings is dependent on how proficient you are on the game. For example, Poker requires skill and not just some luck like slots.
A friend of mine who always wins from online casino but now he is more confident he always gambles with risk. On the other hand, he has a lot of money that he has won through gambling, so it is easy to become confident if the capital is high.
Your confidence grows with your bank your management. And that is where your friends confidence stems from. And from experience the higher your bets the higher your odds of winning.