A stock portfolio will always consist of multiple stocks. At any particular time, some stocks will perform while others will not perform. Your portfolio returns will be the average of both.
During a good market, your portfolio can give you a return as high as 30-35% (benchmark index nifty50). However, during a bad market- the returns can be as low as 2-5% and even negative.
If you sum up everything, you can expect an annual return of 15-18%, depending on which stocks you have invested. Nevertheless, you can generate even better return if you even the basis of stock market and know how it works.