Depends what engine you use. Like CTR B16B engine, you can only adjust the cam timing a half degree, which is not very much at all. So to 'tune' your cam, basically you need to get a cam pulley (RM500 for a cheap one) and tune it. You either get the power to come in earlier or later. But you can only get so much from a standard cams. Want more tunability, have to go for racing cams.
For very basic tuning, a VAFC unit will help. With proper tuning you can definitely increase performance. This is proven in many cases. If you couple the VAFC with few other things, like ITC and so on, you will get even more tunability. But this is so called 'traditional'. The modern way is, buy engine management system like e-Manage, Haltech, Motec, etc. These units can tune air-fuel, VTEC point, ignition timing, injectors, etc.
The common recipe last time was VAFC + ITC + cam adjustment. All this will work together. VAFC adjust air-fuel ratio and VTEC engagement, ITC helps timing of fuel ignition and cam brings the powerband closer to the VTEC engagement point.
Hope that helps.