Seriously reconsider your decision. If you still want to play...I accidentally a 2015 deck builders toolkit today.
I literally haven't touched a MTG card in over 17 years. What should I do first?
Depends on what you want to do. If you have friends to kitchen table with do that. If you want to play in tournaments like FNM play casually for a bit to relearn the rules, watch a few videos on ChannelFireball, then buy the cards for a cheap tier 1.5/2 deck or draft if you care about winning. Just have what fun you can with the understanding that if you want to win you're gonna have to put a few hundred dollars and a shit ton of time in at the absolute least. The game is as fun as you make it and as expensive as you're comfortable with it being. My current rogue control deck for standard is about $250 and I enjoy it because it's dumb as hell and has main board Pacifism. But there are budget tier 1.5/2 decks you can put together for $50 and easily win a FNM with.
Unrelated but our FNM this week is Block Constructed. The only cards in my deck that I have to swap are 4x Dissolve. Bitches gonna get wrekt this week.