Humphries, who was his side's top scorer with 57, and Rashid, with 43, were dismissed within the space of three balls by Jones but by then they had boosted their side from a precarious 147 for 8 towards a final total of 222.
Glamorgan then made a hesitant start to their reply to finish the day on 39 for 2 with Steve James and Adrian Dale the men out.
Jones, playing only his fourth Championship match, finished with 5 for 31 to improve on his previous best of 3 for 94 against Yorkshire, also at Sophia Gardens, last summer.
Rashid and Humphries came together with Sussex wobbling in mid-afternoon and took advantage of some uninspired bowling and a couple of missed chances to revive the Sussex innings.
Humphries, in particular, rode his luck well. He was dropped by Dean Cosker off a very sharp chance to backward point off Darren Thomas when on 41 and he had added only three more runs before Alun Evans put down a straightforward catch at square leg off Dale. Humphries celebrated his good fortune by reaching a patient 140-ball half-century with a square- cut off Steve Watkin for his third boundary.
He was finally out when he top-edged a hook off Jones and was caught at long leg. Rashid then followed two balls later when he was bowled around his legs.Reuse content