You'll need a sheet of copy paper, and some card that you don't mind using for testing your layout. You won't waste any foil trying out your layout either, as the layout is dry letter pressed onto the test card instead. You only add foil once you've done all your testing and adjustments.
If you're going to die cut the card your design will be on, then leave that until after the foiling, but you just need to have your card a little larger than the die cut will be - 1cm in each direction is plenty. You just need a little card around the edge of the die so you can have straight edges to line up with while you are foiling. You won't need to waste lots of card due to not being sure where one our card your foiling is going to end up.