Predecessor Builds > Sparrow > Sparrow D

Core - Storm Breaker, Sky Splitter, Tainted rounds, Demolisher.
5th item can be Kingbane/Nuclear Rounds or Lightning Hawk.
Last item depends on the game normally ill get dust devil for the move speed or Equinox to help me survive team fights.
if you like crit builds Imperator is also a soild 5th or 6th item depending on your game, Onixian Quiver also a decent item.

R > Q > E > RMB
or
R > E > Q > RMB
i normally max Q 1st for faster farming i dont PVP to often to early but if you do PVP early max your E 1st.

Any 3 of the starting crests are good tbf, i choose Pacifier because i like the dash on sparrow but Eviscerator is prob a better pick.