1 What needs me tell their feast and goodly guise,
needs me tell > need do I have to describe goodly > gracious, courteous; attractive guise > behaviour, demeanour
2 In which was nothing riotous nor vain?
vain > vain; foolish
3 What needs of dainty dishes to devise,
dainty > choice, delicious devise > talk, recount
4 Of comely services, or courtly train?
services > {The act of waiting at table; the manner in which this is done; also: the courses served}
5 My narrow leaves cannot in them contain 6 The large discourse of royal prince's state.
large discourse of > [necessarily] broad disquisition upon