MtG is relatively inexpensive if you play Limited formats (Draft, Sealed, "you play what you open") or newer Constructed formats (Standard). For older formats,

MtG is relatively inexpensive if you play Limited formats (Draft, Sealed, "you play what you open") or newer Constructed formats (Standard). For older formats, which I unfortunately find the most fun, your best bet is online. WotC has an official client (Magic Online) which is Windows-only, bug-ridden and requires you to rebuy your whole collection. There are free alternatives such as xmage or cockatrice.