You can enjoy IWTV as a stand-alone book! You can do whatever you want! It’s your life. 

However, The Vampire Lestat is a response to that story, it’s all the things Lestat wanted to tell Louis but couldn’t, and it only really mentions IWTV briefly. TVL is almost a standalone book but it ends on a cliffhanger, so it makes you want to go on to the next one. And the next, and the next, so that’s sort of why I read all of them. 

I would always recommend reading at least the first 3 bc those are generally, fandom-wide, considered the best.

12 books is not that many when you have a lifetime to read them. I’ve re-read all of them except Vittorio (only 1x for him), so they’re more like 36+ books for me. I read them for different things when I re-read them. People read the Bible over and over and look for different things in it.

Just about any of the books could be stand-alones, you can pick based on which characters you like best. The Vampire Armand could be a stand-alone book, he goes deeper into his story, which he gave in previous books. Some books give a different perspective on previous events in the series (what we call the “unreliable narrator”).

Most stand-aloney:
The Vampire Armand
Blackwood Farm 
Prince Lestat 
Pandora 
Vittorio the Vampire