How to correctly calculate the number of options in pair trading?


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For example, I have pair GDX*231-GLD*145. I want to take deviation and use ATM options for this. I want to buy a put GDX and buy a call GLD. Ratio in this pair GDX and GLD 1.59. Do I need to use this ratio in options? Or I need to correct this ratio using options gamma and delta? Or use one gamma? Or just take options in the ratio 1.59?