Normal MtG rules apply here. You may not assume that your opponent will cooperate with you (e.g. choose not to block any of your creatures when they can). Assume that your opponent will block the largest power creatures that they legally can with as many creatures as they legally can, regardless of whether or not it will kill their blockers (in the event of tied power, assume they choose to block the first of the tied attackers alphabetically). If you would draw a card, you may assume that you draw any card remaining in your library, regardless of shuffling.
It's your main phase 1, you haven't played a land for the turn. You're being demolished by your opponent and they have you dead next turn: reverse the tides and win this turn! You've just cast Three Dreams and are about to resolve it. Good luck!
Field of Reality
Flight of Fancy
Vow of Malice
Vow of Wildness