Ethan Bamber was the pick of the bowlers as he took three wickets in a brilliant opening spell to leave Sussex at 40/3.
Fellow debutant Taz Ali claimed his maiden First Class wicket, dismissing James Coles to claim Warwickshire fourth of the day.
Tom Clark and John Simpson then combined with both players scoring centuries, but the former fell to Ed Barnard late in the day, Kai Smith claiming his first red-ball dismissal behind the stumps.
