He received a Bachelor of Arts from Baylor University in 1978, where he graduated magna cum laude.

[4][7] After graduation from law school, Gilstrap entered private practice in the town of Marshall, Texas as an Associate with the firm of Abney, Baldwin & Searcy from 1981 to 1984.

[8][7] He later became a founding Partner of Smith & Gilstrap in Marshall from 1984 to 1989, where his practice covered oil and gas, real estate, probate law and occasionally patent cases.

[5][8] Gilstrap was rated as Unanimously Qualified by the American Bar Association and had a hearing before the Senate Judiciary Committee on July 28, 2011.

[22] October 2021 reporting by The Wall Street Journal revealed that since 2011, Gilstrap had presided over 138 cases in which a familial financial conflicts of interest allegedly required his recusal.

[40] The paper's investigation revealed he held the national record for number of cases in which a federal judge did not recuse himself owing to an alleged familial financial conflict of interest.

[41] However, the investigation also noted that Gilstrap had not taken any action (and certainly not any biased action) because virtually all of the cases at issue settled by agreement of the parties, prior to the defendant filing an answer and prior to the Court making any ruling on the merits.