Of course you need to watch season 1 and 2 before watching season 3. It's not an anthology series.

It's not continuing any specific story of the first two seasons but I don't think you'll care for it much without knowing the relationships, personalities, and backgrounds. This first episode of the revival is a lot of catching up with the old characters and I think a lot of it would fall flat for someone who has no idea who any of the characters are. This premiere at least is definitely for people who know the show.

There are only 20 episodes total that are less than a half hour each prior to the revival, so no reason to not just track those down if the cast or premise appeals to you. This is a week to week release anyway so plenty of time to spare to watch the original ones while this comes out. If you're in the US, the first two seasons are on Hulu.