https://tappedout.net/mtg-decks/budget-beginner-teaching-decks-1-green/
https://tappedout.net/mtg-decks/budget-beginner-teaching-decks-2-red/
^^ the two decks I used, I played green and the ai was red. Still getting the hang of this game but with over like 50k cards in the library and endless combos it's so deep. The AI is quite smart on Forge too. I've never played MTG in my life so this is all new to me.
One of the big things in Magic is formats, releases of new cards are called sets and those sets can be legal or illegal depending on which format you use
The most basic format is Standard, which means only the 4 most recent sets are legal to use in your deck, another popular format is Modern which allows every set after the 8th Edition to be played
There are exception (notably ban lists) to these
Formats are easier to balance than the entirety of the game since release (although the devs frequently fuck up the balance)
If you want more info : https://mtg.fandom.com/wiki/Format
Standard rotates every three years now, which is kind of nice. It used to be too short IMO.
It can be double edged tho, if the sets are whack you're kinda stuck with it
I dont follow competitive Magic too much these days, but I remember the community was seething about Throne of Eldraine at the time
They introduced a new format (pioneer) that seems to be about the same rotation that standard used to be (~4 most recent sets). I very recently just got back in so I'm still learning about a bunch of the stuff I missed. I think those format changes just happened.