In the past, I have never used any kind of sealant on my valve cover gaskets. For the most part, I haven't had any leakage problems to speak of but there were a couple of occasions where I did. I am about to install my valve covers on my new engine so I think I will use sealant this time as I don't want oil dripping on my new headers. So, what sealant would you recommend for valve cover gaskets?

You shouldn't need any sealant. If you have decent valve covers and good gaskets for the application, it shouldn't leak.
A lot depends on the heads and valve covers you're using.

As was said a good set of valve covers and gaskets should do it . but i have had a leak on a set of super performance valve cover gaskets due to them just wearing out i use rtv blue on the section that wore, and it did the trick ....i'm needing to order another set of gaskets.

I like to use an adhesive to hold the gasket to the cover, and then a thin film of oil or grease on the head to allow the cover and the gasket
to be pulled off later on, hopefully without ripping the gasket so they can be reused a few times.

Same here

I've been doing the same as Zippy for decades - no leaks, and the gaskets (FelPro cork) release from heads cleanly.
I pretty much always glue a gasket to the removable piece & grease the side facing the block/heads, so any future cleanup keeps debris out of the engine.
Carb gaskets I just grease both sides.
Just a thin smear will do it.

I use Permatex high tack spray a gasket on pretty much everything https://www.permatex.com/products/g...x-high-tack-spray-a-gasket-sealant-6-oz/

I also started using valve cover studs instead of bolts so I know the gasket is where it needs to be.

i like studs on the removable engine parts [if possible], such as headers, carbs, oil pan, etc.
even a couple of short studs on the back of the block to help get the [automatic] transmission in place before it hits the guide pins. i have found these to be super helpful for me. others may differ.

From everything said above, the most critical factor is FLATNESS.. the cover and the head casting. Next, is the clamping load... must be equal and not excessive.. excessive clamp load causes the gasket to split... as well as using grease or oil upon clamping.

Always best installed DRY, especially rubber type gaskets. The gasket does the sealing... not the chemical.

I worked for many long years for a major gasket company and was responsible for all the installation instructions.

Glue the gasket to the cover with Gorilla Snot (3m trim adhesive). Oil the other side if the head isn't already oily (usually is lol)