Hi Bala H,
I will provide an answer following my previous knowledge on that particular topic.
The Great Gatsby is generally about the 1920s society in which everyone is after accumulating wealth. Gatsby is part of that wealth-seeking society. He is inspired to gather riches through "bootlegging", which means selling illegal drinks at the time.
Stating whether Gatsby's deeds are moral or immoral depends on how one defines the term "moral".
If one considers the Pragmatic meaning of "morality", they would view Gatsby's action of selling illegal drinks to gather wealth as "moral" as long as Gatsby is part of his society whose only concern is gathering riches and competing with the richest people. The means to attain wealth then do not matter; what matters most is attaining the goal.
The Deontic view of morality, however, would consider Gatsby's way of gathering wealth as immoral because he attains such goal through Machiavellian means. In this perspective, it is not the goals that matter but how moral the means to attain the goals are. In this sense, gathering wealth through immoral ways is simply guided by selfishness and ill-conduct.