Please read fault codes before you start changing parts randomly. Not even a Fiat needs each sensor changed one by one , they were made to last the lifetime of the vehicle. Doing so will cost an arm and a leg, the result is that the car does not work and issue is not fixed. You don't change part based on superstitions or beliefs.
So engine does not start at all ? Read fault codes, take it that to a mechanic who can fix it for you. Good that you changed spark plugs and leads, that's probably the right decision, and well the ignition coil pack could also need changing but anything else is just useless to do without proper diagnosis.
