I think it's unusual for the "new set constructed" Midweek Magic event to start the same day as the set comes out. If you want to play in the event without spending a lot, here's a mono-blue flash deck I threw together that (a) uses no rares and (b) uses a lot of cards you might already have from earlier sets. I obviously haven't tested it. Might be terrible.
4 Opt
3 Unsummon
4 Spectral Sailor
4 Brineborn Cutthroat
2 Essence Scatter
2 Negate
3 Into the Roil
3 Think Twice
4 Faebloom Trick
2 Cancel
4 Refute
3 Tolarian Terror
2 Demolition Field
20 Island
If you luck into opening any, I would slip in Sphinx of Forgotten Lore or Voracious Greatshark in place of Tolarian Terror, and Crawling Barrens or Soulstone Sanctuary in place of Demolition Field.