how long it took google to gather data and display ads that targeting us ?

i know the ads that display in adsense website not always relate to that niche ads but also user browsing history. i notice that when you clear your history etc. most of time you will get random ads especially the ads has this text " search result " like from shofast morery. how long it will take until google get accurate data and targeting us ads from our interest

all are processed by AI very quickly, when the AI reviews your ad, it is approved or not

If creatives are approved, it's usually right away pretty much. Make sure your bids are high enough. I have myself often forgot to place a bid and the default 0.01 just doesn't serve ads.
Note that I've observed that in the first day or two, the system over-delivers. You'll get much more impressions and then drops off to a more stable level day to day. This I think is so that the system takes less time to determine your quality, it just needs the data or as others would say, learning.