How to fit an LED transformer / driver
Some LED's just won't dim, or dim well. If it didn't say dimmable on the package, it probably isn't. G9's are typically 120v, so they shouldn't need a driver unless you bought something that is low voltage (12 or 24v). You may need a better or worse dimmer. 

First check with the lamp manufacturer. If they are reputable they will have a list of commonly available Dimmers and the model you should use. 

Second check the dimmer doesn't have a minimum load requirement. Many "Smart" dimmers (fade on / fade off / preset types) have a minimum wattage you have to come up to before they will work properly. 

If all that pans out, you still could only get a small dimming range. Smaller LED lamps like G9 may only dim about 50% and you may get flickering at it's highest and/or lowest setting. 

If there is no suggested dimmer, than try are really cheap slide or dial dimmer. Most cheap LED's were designed to work with the most basic dimmer. If that doesn't work, you may need one of the most expensive ELV type dimmers. 

Additionally, some of the better "LED" (aka CL or C-L) dimmers may have trim adjustments to you can limit the dimming slide or dial range to only be responsive to what your lamp can do.