In my opinion, I think you should read the novel first to have a better understanding of the story. I actually knew the story through the anime first and it got me totally hooked. But in the anime, there are some parts that are not explained as well and as detailed as the novel. As far as I know, the manhwa is the most similar to the novel compared to the anime and The Untamed. Honestly, I think you definitely have to watch and read the novel, manhwa, anime and The Untamed cause they are all amazing.
Long story short, I think you should read the novel first to understand the storyline better.
^ I agree with the commenter above. The novel has so many details that aren't included in the rest of the stuff. I would recommend reading it first (I binge-read it in less than a day even though I read the manhua first and regret it). I think watching Untamed or watching the anime could be last in your list of to-do, mainly because you'll miss out on the romance parts especially in The Untamed. That doesn't mean you shouldn't watch it as it is still really good, but could be put on the back burner for a bit.
I would recomend the anime first. Though it is true that the novel is better and in more detail and makes you understand the anime better. BUT i did like the whole introduction and easy going wei wuxian of the anime so much, that it bleed into my immagination while reading the novel. I think i wouldn't like wwx and lz as much if i startet with the novel.
So i woul recomend to start at least with the fist few episodes of the anime to get that fun feeling of wwx and lz and the sounds of their respective instruments.
Should I read this first or watch the anime? Or watch The Untamed? I've been wanting to start but I don't know how because there's three different things that I could do, either watch The Untamed, MDZS or read mdzs and I can't seem to make up my mind. Also, I don't know which among the three would be best done to understand the plot and story best
(also the novel, should I read it?)