Apart from Lichtsteiner Emery's transfers have been decent so far and even then that was just a cheap squad filler signing. (he did prove to be well **** though) And we probably would have got away with how awful he was but for Bellerin's career threatening injury.
If Emery manages to boot out and replace Ozil, Mustafi and Xhaka with decent hungry players i'd say he's had a great summer. Those 3 sum up the end of the Wenger era. Huge transfers for ordinary players. Xhaka was Wengers choice ahead of Kante, shocking stuff.