Needs a lot more sanding before, you can apply any stain.

If you want the easy route? Paint the treads and the riser. Add a runner and call it a day.

Sand the heck, fill the holes.

Or............get new treads: )

I need to see them from much further back very often carpeted stairs were never meant to be uncarpeted. I do agree the best you will get out of these is sand , fill, paint and add a runner .

The treads look like oak to me, but I'm not an expert and the pic isn't great.

whether or not to stain/paint depends on how everything else looks.

Spindles, trim, wall looking perfect?

It's all relative.