Avocado, broccoli, spinach, lean turkey, skin free chicken, fish, almonds, pretty much any fruit you want and shitloads of water.
Eating these types of food on a regular daily shceme in combination with lifting as often as you can and proper sleep will keep you lean but let you gaiiiiin brah.
You can eat some other stuff aswell, unless it's clearly not healthy, oh and to keep your metabolism and keep you sane you should have a cheat day where you can eat whatever the f you want as long as you keep it in regular sized portions.
I don't got any experience of this, yet. But from what I've read and heard from people it have clearly worked for I would say it's legit.