You cannot out-train your diet. That is so, so, so important. Somebody was just saying today (honestly, I forget which post or I'd link to it) -- eating itself is anabolic. If you're training right, and you're properly insulin sensitive, your body is not going to store fat when you eat food. It's going to build muscle. I'm not saying anything mysterious and amazing when I say if you start at 3500 calories a day, and then hit 750mg/wk of T, and don't increase your calorie intake, you will build nothing.
Because of this, I'm going to go with 3J here and say diet is 80%. Now as for that other 20 percent, how much is training and how much is gear? Well, I think there's a lot of variables here. Gear is not the same from vendor to vendor -- some of it is shitty, some of it is outright fake, and so on. By the same token, some dudes think they're training awesome, and they can't even break parallel squatting. So good training is super important (along with rest!). I am inclined to say that gear is either 5 or 10 percent here, but I don't have any experience with it. It's certainly not more than training because if you sat on your ass with a perfect diet and did a snorkels-style cycle, you'd get nothing. If anything, that says to me 80/10/10.