Anything with two cores, 1GB of RAM and 8GB of internal storage is more than enough if you're going for an Android fagsmartphone, unless you're some 4redditor who wants to post epic memes on Facebook or play shitty games on his touchscreen toy. You might also want to check the quality of the camera, it turns out to be very useful after a lifetime of not having a phone.
This will suffice as long as you install only what's necessary (IM, Uber, and the like). Make sure you buy anything manufactured in the last two years that costs less than $300. Anything more and you're wasting your money on an octa-core Facebook device.