Mini solar panel to DC motor
After some research I found that I needed a inverter. My question is:
  do I really need a inverter? if I do what inverter should I get?


You actually need an MPPT tracker also called a solar charge controller. This helps match the voltage and current (that act like a diode) to the load of the motor. The solar panel needs to produce more power than the motor uses. So if you have a 10W panel, it could run a motor using less power than 10W. The controller takes some power (usually 80% to 90% efficient) so that means you could run an 8W motor with a 10W panel. The 10W also assumes that your at the equator (1000W/m^2 of sunlight) and that the panel is pointed directly perpendicular to the sun on a sunny day. At higher latitudes you would get about 600W/m^2. So a good rule of thumb would be 3 to 6 times higher panel than your load. 


Source: http://www.solarjourneyusa.com/learn-buy-equipment.php