If cost is the main factor and you want to get into the airlines, I would do your training modular and follow some advice on this forum. Keep your CPL/IR training at one school, really research where you do your JOC/MCC course and work as hard as you can in your ground school, flight tests, MCC etc. There is no shortage of qualified fATPL holders looking for airline work, there is always a need for QUALITY applicants that can cope with the demands of a Type Rating. If you are motivated and willing then you will succeed.
I wouldn't necessarily bother with an FI rating unless you have no problem spending the money doing it or have a desire to be an instructor.