I want to get adsense on my personal site because I have a lot of original information. I've applied for adsense but I keep getting denied explaining "lack of content."

I heard that if you have a valid adsense account - you can post ads on any of your websites, all you have to do is add the url in your account. Is that true? If that is true - would it be possible to just make a fake blog website with a ton of bs content to get approved so I could use adsense on my personal site? Like would google check and see if my personal site (which has already been denied) has enough content?

Kindest Regards,
Foxyy

Yes, once you get approved you could theoretically add the site taht didn't make the cut. However, that site obviously doesn't make Adsenses terms of use because they already told you it lacks content. Adsense may ban you in the future. I advise taking a few hours and sprucing the site up, writing a few articles etc. If not, make a new site and write some. You should be fine.