Intake, Headers/Exhaust won't show high gains on a small displacement & economical engine like the single cam Y7, nor will an aftermarket camshaft as people think.
You're just adding bling to a snail. If you do get I/H/E and an aftermarket camshaft you'd only be getting up to a 15hp gain if you spend around $800. You can instantly gain a good 20hp if you spend a few hundred and do a y8 vtec mini-me head swap, and add the I/H/E an aftermarket camshaft above that, you'd still only be making around 130-140hp above the stock y7 106hp (estimated $900~$1600)
If you want power, do a swap, turbo, or rebuild the motor from the block and up because you won't be getting much out of a bone stock y7. Your question is like asking this:
I HAVE A GROCERY CART, HOW DO I MAKE IT FASTER.
Save up for a swap, if I had the money i'd do an H2B or do a CRV-tec.
Libertariat said:
You might get 5-10whp out of a camshaft on a d-series, but an H23 or a B20 will see ~20-30whp and 10-15wtq from a set of cams.
Honda-tech sticky "
Just Bought a Civic! How Do I Make It Faster?"
http://honda-tech.com/showthread.php?t=2915974
Intake POD/Cone filter HP gain myth busted (MightyCarMods)
http://www.youtube.com/watch?v=PAIxeQUSg-Q
The best exhaust on a Civic for under $200
($40 univeral muffler
Dynomax Super turbo + custom piping on an H2B)
http://www.youtube.com/watch?v=fzvl6-_lWIE
Remember, the definition of Civic is "Of or relating to a city or town, esp. its administration; municipal."
Synonyms: "civil - urban - municipal - civilian - town"
It wasn't built to be a race car, it was built to be a commuter, it's a matter of you building it up to what you would like and restricting your modifications to the stock motor won't give great results.