I haven't played with them myself so I can't be sure, but the brand new "jumpstart" product looks awesome for new players to me. https://magic.wizards.com/en/articles/archive/news/introducing-jumpstart-new-way-play-magic-2020-02-20
They're little themed mini-decks that are designed such that you can combine any two of them to make a new deck. It sounds like a great way to give a new player a taste of constructed. A new player can play a couple rounds with some of the mini-decks and get a feel for what sorts of cards they like, then put them together in any combination ... they get to build a deck that's actually their creation, without the incredibly intimidating barriers to building your first MtG deck, like getting the right mix of lands/spells/creatures. I don't think there's any other packaged MtG product that can really do that.
I like the idea of starting someone on that, though I can't speak to how much gameplay you can get out of them before you'll want to move on to something else.
The greatest memory of magic I have is when I first started playing... Like the day or two of. Basically my deck was just every card I owned. One of the creatures had a fascia peel and I couldn't even read its stats. We would just play at the kitchen table, like 4 of us. Sometimes 1 on 1 at the picnic table at the park (no sleeves). This product reminds me of capturing that moment.
The pre-cons I enjoyed the most, and always recommend, were the Urza block With themes like Enchantments that “woke up” when something was cast, or cycling, reanimator, EhrnamGeddon, mono-Black discard, to u/w control. They had it all. ( a bit pricey now and sometimes difficult to find the more affordable opened decks)
Over the years they were less interesting and they discontinued the tournament packs, which were GREAT, but the worst had to be the intro decks. I believe started with Shards and ended in Lorwyn block.
Anything prior to that is decent. Only problem is they aren’t cheap and, like mentioned in an earlier comment, you’re better off just getting jumpstart..
Unless you really want the nostalgia
For nostalgia I started picking up middle school cards. I can’t really afford Academy Rectors or Mox Diamonds, but 90 cent Spiritmongers, 2 dollar Exalted Angels and Vindicates, and 30 cent Psychatogs will do!
It’s funny how people go wild over cards that destroy Planeswalkers. Meanwhile Vindicate has sweet art and is sitting in the dollar bin
@desolutionist if you're looking for more advanced play, I like the new Challenger decks. They're a great way to capture Standard feel.
If your looking for the most basic stuff, like REALLY basic, to teach, Open House decks are awesome (don't know how you can get'em during pandemic, but maybe someone has a few to sell on eBay?).
Other than that I'd go with Jumpstart, like people said here, or Duel Decks seem fine.