A lot of people suggest TNG, but I actually recommend the TOS movies. Start at Star Trek II: The Wrath of Khan, watch the movies in order. You can skip the 5th movie without much loss.

Watching the movies will give you enough knowledge to understand why the original crew was such a big deal, even being referenced in universe later. It also gives you a basic understanding of augments, which do come back as later plot points.

Then watch through in order. TNG, skipping some of the junk episodes. Then DS9, then VOY. If you want to watch the TNG movies, I'd say skip them except for First Contact. First Contact is a bad Trek movie, but it's watchable and at least puts it's budget to good use. It introduces you to Picard's famous memed meltdown and it introduces the borg queen. If you watch it, and are going to watch ENT you need to watch the movie first because there is an ENT episode requiring having seen it to fully appreciate.

I personally like ENT quite a bit, aside from a few of its more egregiously bad or boring episodes, it has plenty of pretty good episodes.