The correct reading is "All you need in this life is ignorance &
confidence; then success is sure." The quotation is from a letter to
Cordelia Welsh Foote of Cincinnati, written on 2 December 1887. Mrs.
Foote was then performing as a reader of selections from Dickens,
Thackeray, Hawthorne, Mark Twain, and others. In fact she clearly used
the letter Clemens sent her as something to read on stage. On 26 May 1888
she thanked him for it:
        Dear Mr Clemens
        I want to thank you for answering my letter (you have probably
forgotten it) so promptly, and splendidly--and to tell you that it has
helped me much, the "Half hour with Mark Twain" is a decided hit--and
when my audience are up to the point--and I recite "Jim Wolf and the Cats
*you* are considered the King of comedy-- I thank you--I thank you--and
so does Mother Fairbanks--always
                        respectfully and gratefully
                                                Delia Foote
        Ridgeway ave--Avondale, Cin----

Clemens has written on the envelope, "Complimentary--from Delia Foote."
It's a fair guess (but just a guess) that Mrs. Foote is related in some
way to Mary E. Foote whom Clemens knew through Mrs. Fairbanks in
Cleveland. The letter makes clear that he has known her since 1867 when
she was "a singer of plaintive Scotch ballads that were full of
heart-break and tears." The letter itself was published by Benjamin
DeCasseres in *When Huck Finn Went Highbrow* (1934).

Bob Hirst