So if you were with a rogue would that rogue get a sneak attack?
No. The text says
you have advantage. If it applied to allies, it would be worded to refer to you and your allies, e.g. "When both you and your illusion, or one or more of your allies and your illusion, are within 5 feet of a creature that can see the illusion, you and any such allies have advantage against that creature, given..." etc. As it is not worded so, we can pretty reasonably conclude it's done.
As for what exactly the illusion does, that seems to be up to GM interpretation. It "mimics your gestures", but you can also order it to move--it would be pretty useless as an illusion if that order didn't include illusory running that you, yourself, didn't have to do. That implies the illusion can do things you aren't personally doing/saying--but it specifies nothing further, meaning it's up to GM adjudication.
In my group, Hussar has been a pretty open-minded GM (as he is with most things!) with our Trickery Cleric. It hasn't been insanely powerful, but it has proven useful. Usually, enemies interact with the illusion soon enough to reveal its nature--but then that creates the new opportunity, of swapping places with it seamlessly so now they ignore you and go after your illusion. Overall, it's not the most useful thing ever made, but it has clear uses, especially when a fight breaks out in a large room where we might move around inside it, but we aren't moving
away from it.