What's underneath the carpet could you do a wood step . I would stain it all a darker color if the railing is small

There is only plywood below the carpet. Trying to keep the cost down but still want it done right..

if the plywood treads and risers are in good shape and there are not too many gaps etc... you can fill, sand, and paint them. paint a dark color such as a dark brown. Then have a runner installed through the center and leave about 3 inches showing on each side. Then paint the spindles and the side molding white. Leave the hand rail or re-stain darker or paint dark to match the color you paint the edges of the treads and risers.

Get your carpet runner from a discount shop or find a shop with a roll end. You only need about 3 feet wide so you don't need a long piece of carpet. You can find it very inexpensively it you search around.