Thanks. that is so informative.Capital gains are only from sale of stocks (or other assets), so there is no need to add the word "sale", but "capitals gains from stocks" would be fine. It sounds rather technical though, and "money from stock trading" may be more appropriate.
People also invest in stocks for the dividends they produce, which is something different from capital gains. If you mean to include dividends as well, then you would need a different term.
Are you looking for a term specifically for stocks, excluding bonds, property and other investments? "Money from investments" is a good general term, but this would be taken to include bonds as well as stocks, and it could include property and other investments as well, such as works of art.