How to upgrade the performance on my ford focus?

ok so first off let me make it clear that yeah i know this car isnt the best to upgrade or that it has much potential but honestly i am fine with whatever boost I can get. I have a 2012 ford focus SE. That means 2.0 I4 with no turbo and everything is stock (also stock power shifter). What can I do do increase horsepower and torque? I've read about throttle body spacers, ecu chip upgrades, cool air intakes, even "superchargers" however the "superchargers are just filters that have fans built in to compress the air (do they really work?). I'm new to all of this and am willing to learn. Yeah I could have picked a better car but I'm a poor college student. I'm lucky that it has leather interior and premium wheels.

Read more: How to upgrade the performance on my ford focus?