Introducing QFT. A Guide to Self Study.

Consider reviewing collisions and scattering in classical mechanics and QM. Griffiths reviews classical scattering in his Intro to QM. He covers scattering in Particle Physics in his Particle Physics book.

Supplement QFT with Griffith's Particle Physics book. 

The best place to start is David Tong's lectures, lecture notes and problem sets. These include many helpful warnings.

http://www.damtp.cam.ac.uk/user/tong/qft.html

Then Ryder, supplemented by Zee, to transition to the path integral approach.

There is also a book titled "QFT for the Gifted Amatuer" that moves through the same material very
slowly with a lot of calculations. It's almost too much because you can lose sight of the big picture. So keep Tong's concise notes nearby.

And this begins with a relatively straightforward introduction to Path Integrals. It also has a nice bibliography.

http://www.damtp.cam.ac.uk/user/ho/AQFTNotes.pdf