Johnson's celebration of John Lade's reaching his "Coming of Age" is a light-hearted tour-de-force set of instructions to a wealthy young man for living life to the full. This catalogue of wealth and freedom would not have appealed greatly to John Lade's mother, Lady Mary Lade.
The premise of the poem, of course, is that the 21-year-old Lade now has access to his father's, Baronet Sir John Lade, fortune, with no parental control over how to spend his father's fortune:
Pomp and pleasure, pride and plenty/Great Sir John, are all your own.
Johnson's playful diction includes a clever use of alliteration and, most important, establishes the paradigm for Sir John's future life: pomp and pride go with his knighthood, a heady way to start life at 21, and pleasure and plenty reflect what Lade's fortune affords him.
In the second stanza, Johnson continues his onslaught on moderate behavior:
Loosened from the minor's tether,/Free to mortgage or to sell,/Wild as wind, and light as a feather,/Bid the slaves of thrift farewell.
Most of Johnson's poetry is characterized by very formal latinate diction. What is obvious by the second stanza is that Johnson's advice will not require latinate diction--there will be no philosophical injunctions that life is fleeting and one must be cautious. Instead, Johnson uses, for the most part, Anglo-Saxon vocabulary to advocate that Sir John spend his time on basic joys--"wild and wind, and light as feather."
Johnson's third stanza was absolutely not designed to comfort Lade's mother (or his aunt, Hester Thrale, Johnson's friend) when he advocates lining up "Bettys, Kates, and Jenneys" and "show the spirit of an heir." So far, there is nothing even remotely redeeming about Johnson's advice, and we might be tempted to conclude that Johnson wrote this as a fantasy piece, reflecting on what life might have been for himself had he been born into Lade's circumstances.
The closest to a warning comes in the fourt stanza:
All that prey of vice and folly/Joy to see their quarry fly,/ Here the gamester light and jolly,/There the lender grave and sly.
Still employing largely single syllable Anglo-Saxon vocabulary, Johnson does manage to warn Lade that numerous people spend their lives preying on "vice and folly," but, unfortunately, Johnson doesn't go so far to tell Lade that he needs to be careful. Again, the diction and tone are light, playful.
The next two stanzas undoubtedly made his mother and sister cringe. Johnson explicitly advocates that Lade let his fortune fly to the "jockey" (horse-racing) and the "pander" (women). What is worse, Johnson warns Lade against spending his money on houses and land--they are only "dirt, or wet or dry"--advice that is directly counter to the normal conservative approach to spending that would ordinarily be expected from Dr. Johnson.
The serious warning finally appears in the final stanza, which makes everything that came before closer to tongue-in-cheek advice: although Johnson tells Lade to ignore the advice of his mother and guardian, what he really means is to heed their advice so that he doesn't end up hanged or drowned.