Oil on spark plugs

2014 CX-9 Touring
I have a 2014 with 52k miles and decided to change my plugs because mileage has dropped off the past year and there's a gas smell from the exhaust when I first start it. One plug in the front had oil on the insulator like the o-ring is leaking but 2 in the back had oil on the threads and all plugs looked like they had 100k miles, threads were black on all. There was also some oil around the ports when I took off the plenum. Any one else experienced this? Its running better now and no gas smell. I'm going to order a new PVC valve.
I had a friend on a different car that had a bad valve cover gasket, and when he removed his valve cover he noticed his two middle spark plugs were literally soaking in an oil pool. Not sure if this is your case or not but thought this may gave you a lead.

See if you have the same symptoms as mentioned on this video at 1:32 (oil on spark plug)

I should add that 52k miles seems pretty early for that to happen though.
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08 CX-9 GT FWD
I doubt its valve cover gasket(s). I've not seen or heard of any valve cover gasket failures or leaks on ANY CX-9, including my 11 year old 103k mile engine.
Periodically, I clean my intake tube and breather hose (the hard plastic hose). Remove breather hose, air box, clean out the intake parts. If I didn't ever do that, probly would have your condition. Wouldn't worry about it too much. Just put new plugs in and gap them correctly, new intake manifold gasket set and you're good. Cheers