I'm looking to play casually (in person) with some friends and we were wondering what the cheapest format to start buying for would be? And what might be some good pick ups (we have the starter decks but want some more variety) thanks
Pauper is the obvious answer. It's unique in that every card in the format is Common rarity, so that mitigates price already. Check out MTGGoldfish's Metagame page for Pauper, which lists competitively viable decks and their price. Not sure how up to date it is, but it's a good starting point!