Gifford seems to have performed ministerial work in Nottingham in 1725, and to have been assistant to his father at Bristol in 1726, in which year he was invited to become pastor of the congregation in Devonshire Square, London.
He declined the position, but at the beginning of 1730 he accepted a call from the Baptist meeting in Eagle Street, London.
With influential friends including John Ward, one of the trustees, he was appointed assistant librarian in the British Museum in 1757.
Two of Gifford's sermons were published, one on The Great Storm in 1703,' 1734, and the other, preached ten days before his death, To the Friendly Society, 1784.
He edited for the Society of Antiquaries Folkes' Tables of English Silver and Gold Coins, which was published in 2 vols.