You can make a chart show the top 20 Items with the highest sales by using a calculated dimension. Use this expression in the calculated dimension:
Name the calculated dimension "Top 20".
The easiest way to make that chart also show Gender, Size, or Category is to make those things a secondary dimension. If it were my report I would put those things into a cycle group and make the cycle group the secondary dimension. Then, your report user can click through each secondary dimension.