In order to understand the fundamental basics of this deck and its construction as it appears to me, the best way to exemplify this will be taking a short look at my adventures at GP Paris and go from there
Cheap answers like [card]Swords to Plowshares[/card], [card]Get Lost[/card], [card]Seam Rip[/card], [card]Oust[/card], and [card]Portable Hole[/card] deal with early creatures before they become a problem
Once I got a nasty Yue
If you want a casual Aurelia deck capable of taking a bunch of extra combats, I have a sample list you can try out on Moxfield
Play Style: Blues strength lies in its ability to counter spells , draw cards , and control the battlefield with bounce effects (returning creatures to their owners hands)
Build up your forces with Lathril and sacrifice them to effects like Ashnods Altar or Phyrexian Altar for the mana to hit your opponents with a large Return of the Wildspeaker or Walking Ballista