I almost always rush Wit's End or Ionic Spark. Maxing E dominates most lanes and gives you an incredibly fast jungle clear.
CertainlyT's full build Cho'Gath:
Merc Treads or Mobility
Aegis of the Legion
Stack of wards
I feel Cho'Gath is at his best in kite/counter-initiate comps, so I don't usually fear being kited myself.