There's also untap.in which is browser based and free. but you need to pay if the players are above 4. I used to use that for our edh game sessions. Last time I had fun was with Winota, too bad she not good on current meta now.
Step 1: Fog Bank
Step 2: Followed Footsteps on Fog Bank
Step 3: Stall for Fog Bank Copies
Step 4: When ready, overwhelm enemy with 100+ Dragons
Shocked Followed Footsteps is not a more expensive card.
This one is from the new set and it costs more than twice as much. Although, it does only cost 1 and 1B mana, but appears they would work similarly.