In answer to your question (because tiddy's crying because I'm being mean to you)...
Engines need air and fuel.
After combustion, exhaust gasses then need expelling from the combustion chamber.
It's a very simple concept. The more air you can get in, (and the more fuel you add to "match" this increased airflow), and the more efficiently you can remove exhaust gasses, the more power you make.
So, on a budget:
Intake - good quality/high flowing panel filter, and resonator removal.
Exhaust - equal or un-equal length headers, good dump pipe (butler), and 3"
TBE.
Tune - to notify your
ecu of aforementioned modifications.
Obviously lightening internals, upgrading bearings, turbo, intake manifold/head work, cams, stroking etc. are also going to increase performance, but aren't cheap.