Gears will make your car FEEL faster, but really wont do that much to actually make it faster. A good lock up converter makes a big difference, and it will act the same as your stock converter on the highway. If a converter is out of your budget, or just not what you want right now, consider going with 3.73 ratio gears.
If your car is a DD, and highway RPM/Mileage is a concern, check out this link to calculate your cruising rpm with different gears/tires:
http://www.f-body.org/gears/
Ex....w/ 26" tire....
3.23 ratio = 2050 rpm @ 70 mph
3.42 ratio = 2200 rpm @ 70 mph
3.73 ratio = 2400 rpm @ 70 mph