Single Sink to Double sink plumbing in bathroom

I’ve read through many threads on this site about his topic but none have completely clarified the proper way to fix the problem I’m encountering. Trying to upgrade from a single sing to double sink vanity but my main drain isn’t where the sink goes its over by the toilet. Any advice is greatly appreciated. Trying to figure out the best and most cost efficient way to go about this. I attached two pictures one of the existing drain and one of what I had planned to do.