True you can get an idea about what is going to happen next on the market based on different events, acts, situations ( the basis you are talking about). So eventually, you are saying that you can predict what "may" happen based on the basis which all goes back to probability. Your probability of something to happen depends on the event that took place through which you can predict the price. Then, how come you are saying there is no basis when it comes to gambling? When a person has, lets say, 1% chance to win a bet, then if he loses 99 bets straight in a low, he can pretty much predict that his 100th bet is going to be a win. That's the basis for him.
"In gambling, you can predict without a basis". I didn't say we can't predict in gambling. Assuming that you can win because of a losing streak, there's no actual basis on that. The more we lose on a game, the more we think there might be a chance to win. The losing streak boosts the mentality of the gambler to think to be more positive, that's expectation.You are actually trying to compare the amount of risk in gambling vs trading if I am not wrong 
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both have risks but I'm just addressing the other people thought that trading is like gambling, to be more specific on using terms..