I would put in as large a vanity as you can, while still leaving adequate space around the toilet. One sink, and as many drawers as you can get. If that means the sink isn't centered, that's OK.

@AnnKH, that's what we were thinking but just wanted to make sure we weren't overlooking something.

Select the largest vanity and mirror that will work in the area. You might want to consider a banjob top for the vanity.

Please make a simple drawing with the width of your room, how far from the wall the toilet is placed and where the current water lines and drain are placed.

"a sink base with drawer base to the left of it."

Do you have a picture of what this? You want two base cabinets here? You'd usually get a single vanity as large as you can accommodate. You will get more storage out of drawers that reach across the entire front than from a section that has drawers and another section with doors.

Do you have a closet in here?