Here's why:
* "Vamp" is not a standard verb in this context. It usually refers to a type of shoe or to "liven up" something.
* "Had" is used incorrectly here. It suggests a past tense action, but the sentence doesn't clearly state what was done.
* "My winter wardrobe" is the object of the sentence, but the action is unclear.
Here are some ways to fix it:
* "I need to vamp up my winter wardrobe." This uses the correct verb and makes it clear you want to improve your wardrobe.
* "I had to vamp up my winter wardrobe." This uses the correct verb and suggests a past action, perhaps due to needing new clothes.
* "I've been vamping up my winter wardrobe." This uses the correct verb and indicates an ongoing action.