Needs tips effective, proven advice, on how to gain weight. What supps to take?

I lift free-weights, and take a 900+ calorie protein powder. Cytogainer to be exact. My metabolism is hard to defeat. Those with similar experience give me some good advice. What am i missing here?Needs tips effective, proven advice, on how to gain weight. What supps to take?
Nuts are fattening as they contain about 600 calories per 100 gm.

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