It depends. If the portrayal of the yandere girlfriend is done in an interesting and nuanced way, it could be appealing. But if it's overly stereotypical or one-dimensional, then no.
A gift from her in a yandere manga can have multiple meanings. It could be a sign of the yandere's obsessive love, an attempt to control the situation, or a way to create drama and tension in the story. Sometimes, it might even be a red herring to mislead the reader.
Male yandere characters in stories are often overly possessive. They have an intense and sometimes obsessive love for the object of their affection. For example, they might not allow their loved one to have any other friends or interact with others freely.
Well, such a girl is often obsessive and possessive. She might go to extreme lengths to keep the person she likes close to her, sometimes even using violence or threats.
A great male yandere story is 'Diabolik Lovers'. The male characters in this story often exhibit yandere - like traits, especially when it comes to their relationships with the female lead. They are overly possessive and their actions are sometimes extreme in their desire to keep the girl close to them. Also, in some darker versions of fairytale retellings, there are male characters who turn into yanderes. For instance, in some reimagined versions of 'Beauty and the Beast', the Beast can show yandere - like tendencies towards Belle in terms of his possessiveness and jealousy.
One common theme is possessiveness. Male yandere characters often feel an intense need to own or control the object of their affection. For example, they might not allow the love interest to interact with other people freely.