IMO gambling is gambling as long as it's purely depending on luck and no support for it on other aspects "knowing methods of trading, best methods and ways to earn, specific market analysis", if the trader doesn't know these then it's merely gambling.
Well, there are 'gambling' like sports betting that is not purely dependent on luck all the time (I mean to say here, some time sports betting also requires some luck to secure profits). Most of the time usually sport betting dependent on your betting skills and just how much information you can get on the bets. So, I certainly believe trading always does not behave same as gambling. There are lot of factors to differentiate both.