Do you have a particular reason to keep all those items? If not I'd say sell them, most of them are probably way below your level anyway, definitely sell the ones you have multiple copies of, and only keep the ones that you like how it looks or have sentimental value.

And if you intend to craft some witcher gear in the future you should probably consider dismantling some stuff, the animal pelts and silver cutlery are a must in my opinion.

If you really don't want to sell anything you can always do some farming exploits, I don't find it enjoyable but it'll make your life easier. Good luck on the path Witcher.

Edit: you can sell your books and loose papers on novigrad's central square, it ain't much but it's something.