As a gift for someone's 50th birthday, whether a man or a woman, a gift certificate or gift card to the person's favorite store or restaurant would be appropriate. Buying someone an article of clothing may not be ideal since it can be difficult to determine a person's taste.
For someone who loves chocolate, a chocolate tasting tour would be an excellent idea. Many cities offer these types of tours, and they are usually priced less than $100. If the gift recipient is not a chocolate lover, then a regular food tour might be equally appreciated.
If the recipient is a bike rider, then a bike helmet with an original pattern or striking design may be impressive.