Is it better to diet first and lose the body fat, down to approx 15, or is it better to to bulk up first, then effectively cut down the body fat?
If you’re above 15%, it’s generally better to diet down first. You don’t want to be a fat guy getting fatter. At the same time, you seem relatively new to training. Many beginners can actually build muscle while burning fat. Eat to lose fat, train your ass off, and see where it takes you.
When overfeeding, lean individuals will tend to add a greater percentage of lbm over fat weight and fat individuals will tend to add a greater percentage of fat weight over lbm. Most people suggest around 12% bodyfat before overfeeding to add weight (bulking).
I agree. If you are experienced, get as lean as possible. You can then bulk much more efficiently. I cycle my entire training to maximize this effect. But if you do not have the mass, just concentrate on learning and growing.