by bakija
Most of the discard cards are cards you want to use immediately anyway--they get you some VPs (no reason to not take them now) or heal you or something. The ones that cause you damage (Tank, for example) are things you are generally only going to want to buy as soon as it makes you win (and most folks will feel the same way, so unlikely to get bought up).I'm pretty sure at least one "Discard" card (Plot Twist) specifically says you can hold on to it till you want to use it.
So yeah, unless the card says otherwise, you buy the Discard card and use it immediately.