Path Integrals in Quantum Theories: A Pedagogic First Step by Robert D. Klauber
Publisher: QuantumFieldTheory.info 2011
I strongly believe it far easier, and more meaningful, for students to learn QFT first by the canonical quantization method, and once that has been digested, move on to the path integral (many paths) approach. Hopefully, this material will help such students, as well as those who are forced to begin their study of QFT via path integrals.
Science Physics Quantum Mechanics Path Integral Formulation