Whenever a new set begins. this game begins an arms race where only pro players and 12 year olds in their parents basement are able to keep up with the cost of new cards and new decks.
100$ gets you virtual cards 99 packs or 50$ for new decks. These are only virtual so good luck figuring out their convoluted friends interface.
Better just to utilize your non-virtual cards and have a conversation with your friend in person rather than play this game.
They tell you that packs you buy in the physical stores be it game or box store will have codes in them to redeem in MTG Arena, but what they don't tell you is that not all of them do. So it is a guessing game.
Also, game play wise, if you don't have at least 26 lands among cards in your 60 card deck the amount of times you have to mulligan is at least once a hand. And that winning that particular hands drops dramatically every time you have to mulligan. So most players concede before the first play is ever made. Let's talk about conceding as well. Many players will let their turns time out to frustrate their opponent into conceding when it is they themselves that should learn where the concede button is located. I have talked to many other players that become more and more frustrated that a game that is well in hand is prolonged by more than 15 minutes by slow play and educated use timeouts and fuse timers. When it is actual good sportsmanship to concede a game instead of prolonging the inevitable in the most immature manner.
So if you are a lover of MTG, but only a casual player looking for a casual game stay As Far Away from MTG Arena as possible. It may make you Hate all things MTG instead.