This is a pentagram cube, which means you need cards that do one of the three things:

• constant push (create tokens every turn, steal life every turn, Planeswalkers, creatures that comes back, etc)
• mass removal (creature removal mostly, but needed in order to be able to impact the board)
• mass token creation (players needs to be able to develop board quickly and efficiently)

All cards need to give value the moment they are being played and be a threat forcing other players to act.

5 players mean 5x3x15=225 cards per draft, which means the cube should be overall small - no more then 240-260 cards, as we want to have different playstales and decks and not play the same game/draft each time, so about 40 cards per color + artifacts/ramp.