I suggest that you ignore this word and tranlate it into English as "I bought him something". because, it's spoken Chinese, and occasinally, It means not too much; but in most cases, it means nothing. People always like to say that, . eg. if you bought food and say "我买了吃的" ,that means you can speak chinses correctly; but if you say "我买了点儿吃的", that means you can speak idiomatic Chinese (地道的) just like local people. especially, Beijing guys like the word "儿"