We fed on demand and had a consistent night-time routine like PP. My DD wasn't ready for a 'routine' /schedule based on the clock until she was 6 mths old, as she was a catnapper until then. (Any attempt to have her fit a schedule during the day before then was met with a lot of crying, by both of us!).
Being responsive to bub is much more important for their development than a routine/schedule during the first 3-4 months (although most sleep books won't tell you this!).
Edited to add: we did 'feed sleep play' as our routine and bub found her own approximate timings, but it wasn't consistent by the clock.