You wrote correctly that the ability to buy cheaper and sell for a high price plays a very important role in trading, and the influence of luck is not very great there. But gambling can be different. For example, in plinko, dice and roulette, the player does not influence the game at all, but only hopes for luck. In poker or batting, the player has a pretty strong influence on the game and luck no longer has a strong influence here.
Therefore, there are many strategies and tactics, and perhaps even more of them than in the technical analysis of traders.
Now, whether the gambler knows how to bet on these games you mentioned very well or not, there will always be a little effort to make to profit with them but more reliance on luck must happen. So the two have to mix in this, and the same goes for almost all the games in casinos. But not of sportsbooks, at least most of the games could even be more of the function of how good the gambler is in predictions and all that just like how it is in trading. In all, gambling relies more on luck so much that even if the gambler is such that is good at what he does, luck is still needed even if it is just an expression as I like to view it at the end of the winning, the outcome is not something that anyone can predetermine based on how good and experienced they are in playing the games.