Speed isn't cheap.
Intake, header, exhaust, chip, will be your main suggestions. But is 15HP from all 4 of those worth $1,500?
You don't know anything about cars, so I can correct you ahead of time. All the exhausts and intakes you see advertising 8HP gains, 13hp gains, these are either on high displacement cars, cars with tons of engine work or they have forced induction(turbo/supercharger).
Your Accord will NOT see those big gains.
Here's some free speed upgrades, remove weight from your car. For example, remove all seats except your driver seat, remove air conditioning, remove stereo, remove sound deadening material, remove spare tire.
Best bang for your buck is to get new extra light 16-17" wheels with HIGH PERFORMANCE tires.
