I almost think it doesn't matter what you wear with this coat. It is the whole outfit on its own. But that's why I love it so much. I think it's actually best to totally play it down with nothing more exciting than a simple white tee and blue jeans and let it do all the talking (well, aside from the knockout bag, of course).
Whistles Kumiko faux fur coat / in black here
& Other Stories t-shirt / similar here
Zara jeans / similar here