To me, The Next Generation is good for the general vibe of the overall franchise post-original series. Start around season four or even with First Contact for a nicer primer on things if you're totally new to Trek. Deep Space Nine for more of a serialised story but requires a bit of a learning curve. Lower Decks I hear can operate as a good entry point but I wouldn't agree as it's a lot looser with lore for comedy purposes and might give you the wrong idea. Don't start at either Voyager or Enterprise and finally watch with a friend who's more versed in Trek so you'll be able to share in their enthusiasm and ask them about things you might be curious about.