I did the reverse and it worked really well for me. #1 was my airstrip with Missile Silo as #2. You have to upgrade your Oil Refinery to get there most likely (I was able to time it to buy the air strip at 50% off).
The extra plane made raiding oil easier while the Silo greatly cuts down how often you get raided. So its your choice as to which goes first. While I was working on the Airstrip and then the Silo my blacksmith upgraded to Howitzers and Riflemen, these aren't a priority but getting food was really fast and easy. My next priority was my library, adding a third general to my attack helps when I am attacking silo bases. Finally I upgraded my Merc camp, the global merc tanks are great for absorbing silo damage. My primary focus has always been offense,since no matter how much time and energy you put on defense there is always someone who can take your base. My basic thought is if someone hits me for 4K oil that is only 2 or 3 easy raids back to make back, it really is a negligible hit in time.
So on that basis my priorities would be
1) Airstrip
2) Silo
3) Library (research Global tech Command).
4) Merc Camp.
You will need to upgrade your oil refinery, Mills, and maybe your markets to do those four but I thought they were the biggest game changers. 3 offense 1 defense. After these everything helps of course but those four made the largest difference. (if you don't have 3 generals level 20+ then I would deprioritize the library).