like reikoshea said, start with you basics, your typical intake headers and exaust. from there you have a motor that now can breath good, the next step would be either a cam, cam gear, or something a little better, a turbo or supercharger. i've seen good numbers with a forced induction motor. i'm personally taking a D15b and mating a jackson racing supercharger, and i'm going to tune it, change out the cam and cam gear, throw in a chipped ecu, larger fuel ingectors and a high flow fuel pump. really thats all i want and i might be able to push 180hp if i make the correct tune, maybe more, who knows, its all therory. but all in all its all what you want to do.
you have many choices, especially when it comes to a civic.
you could motor swap, build your existing motor, not do anything to it and save, the options are endless. happy decision making!