A Vgs (yes, voltage gate to source) of 5V or less would certainly be great. However if you have any mosfets on hand, look at their datasheets and check the specs on the device.
As the voltage on the gate (compared to the source) is increased (more +ve for N channel, more -ve for P channel), at some point the mosfet starts conducting. For low currents, the device seems to be a resistor. At high currents it is a current source. As you increase the voltage further, the resistance (for small currents -- now potentially a larger current) decreases and the max current (where it becomes a current source) increases. At some point the "small current" can be as large as the device is capable of handling and you can never practically get to the region where current is limited. This final point (pretty much) is the Vgs for the device.
However, as I've suggested, you can quite often use mosfets to switch light loads with gate voltages well under their specified Vgs. If you have any mosfets, check their datasheets and see what the characteristics are like. Determine if dissipation will be a problem, if channel resistance will be a problem, and if the device can actually supply sufficient current. After you've done that, tell us what you've found and I'm sure someone can double-check it for you.
Alternatively, purchase one of the mosfets recommended above. A totally safe bet is any N channel Power Mosfet that is labelled "logic level", has a Vds at least 50% higher than your supply voltage, has a power rating about equal to your motor (this is probably overly generous), and can switch currents at least a couple of times greater than your motor requires.
I'd also recommend a small gate resistor (say 100 ohms). Mosfets have a very high impedance, but highly capacitive gate. When a load is quickly switched, the drain current can be capacitively coupled to the gate. The gate resistor helps prevent the spike from adversely affecting whatever is doing the switching.