You don't want to buy any silicon.
Be sure you are buying airsoft silicone spray or 'food' grade silicone spray. This uses alcohol as the solvent base. Some hardware store silicone sprays (such as Liquid Wrench with silicone) are petroleum based, like WD-40 and will end up damaging your AEG.
You can also look for 'dry' lube or teflon lubes used for motor sports and cycling; these are alcohol based. Be sure to look for the words "Safe for O-rings" before using on your AEG.
Here is one example...
the one on the left: used "gunk" silicone oil i got from a hardware store. The color is a greyish-blue, it was originally black. The texture is sticky, chalky, dry and simply gross and not what it should feel like. Basically, the silicone oil ruined the bucking.
the one on the right: used regular airsoft silicon oil. As you can see, it is still black (as it should be) the texture feels like brand new rubber and is just as good as the day i bought it.