I consider trading as a professional activity. It requires analysis, research and others knowledges. Gambling you just require luck. But yes, maybe there is a thin line between then. It depends on how you do trading.
Yes I agree with you that there is no doubt about this that gambling is a professional activity, trading can be consider as profession, because in trading you need good study analysis and trading skill with previous experience, while in gambling you need just your luck and nothing else.
However you gain knowledge and make trades, luck too is needed to give better profit. The person who get into trade over the past few days need just the investment to buy, the increasing price automatically gives the profit on selling. Here luck is the factor which decides the success. Whether gambling or trading, to certain extent luck is truly important similar to strategies made through researches.