I always put a sealer on the bare wood before staining. Putting stain directly on bare wood will ruin the wood. The color, grain, etc will just be wrong. I am talking about soft woods like what is used for nice doors and trim in houses. Most of it is a pine of some variety. And oil base stain. Belief it or not, with a pretty good match of stain, and good sealer, and timely wiping you can match a new stain to an old stain better than you would think. Of course you put down at least 2 coats of polyurethane top coating to protect the stain. So there are at least 4 layers on stained wood. There have been times when I put the seal coat on a bare wood door and the wood "took the sealer up too fast". If so, I apply a second coat of sealer and let it soak in. I apply the stain before the sealer is dry and in areas only large enough to control the color by wiping. Too light, another quick stain and longer wait. You have to pay attention to what you are doing. I would think that a floor would be a lot of work, for one reason how to stay off of the work.