Re: supplements and diet
Faip has said it really mate.
How much carbs is dependent on how many you will burn. You need enough as you want to gain muscle and you will be burning in the gym but obviously you dont want to overdo it and put on fat weight.
Try to keep the majority to low GI carbs and think about your timings would be my general advice. In other words try to lay off the sugary carbs especially in the evening. Try to go for more protein based foods in the evening.