Oak plywood and the oak wood you will use for edging and other parts will take stain more evenly and at a cheaper price than any other species. Be aware, though, that oak has a very open grain, which will show up more with darker stain. Also, the dramatic grain pattern of oak is something that some customers do not like. Cherry or walnut plywood are other choices, which will take dark stain well, but will be a lot more expensive.
I also am questioning your ability to jump at such a big project if you are a "Newbie" and do not know these things....especially if it is for a paying customer. I hope you know what you are getting into. You could be out a lot of money if the customer isn't satisfied....or, even worse, the customer could be out a lot of money if you botch the job and run. Don't be offended, I am just letting you know what happens for a lot of beginners.
