Hi, I'm new to descent and I want to know if I can play shadow of nerekhall campaign without the core set or if I would need it to do so.

Thanks for your time

You need the core set for any expansion. But you don't need every expansion in order to play Shadow of Nerekhall.

As C2K said, you will need the core set. The nice thing about their expansions is you can get any expansion you think looks interesting once you have the core set, you don't have to go in order of release as they're all independent. This means if Shadow of Nerekhall looks like the most fun to you, you can buy it instead of having to buy all of the previous expansions, which will save you a ton of money. However, I'll forewarn you, you'll end up buying it all eventually anyway...