How do I reinforce a drawer bottom?
One website for furniture plans that my wife recently found is ana-white.com. Best thing is, they're free! Each article/blog post has a materials list and instructions.

There are quite a few plans for near-duplicates of brand-name furniture makers' products.

Here's instructions for a dresser from the website. (I'm not sure exactly what you mean by a wardrobe, since you mentioned it had drawers. When I hear wardrobe I normally think Chronicles of Narnia style.)