You can make the entire deck out of pressure-treated wood, which will provide durability from the elements without any need for paint or stain. Of course, visually, it can leave a lot to be desired.
For a little bit less money, you can add some common wood (Douglas Fir) and it will provide a more finished look. Unlike the pressure treated, you’ll need to protect it from the elements so be sure to budget a little more for painting or staining.
If you want to go high quality at a relatively fair price, I would suggest redwood. It’s going to warp less and is less prone to termite damage. If you have termite problems I’d suggest going with either Cedar or Redwood, the termites don’t like them as much. The redwood can be stained for a beautiful effect or painted, either way you’ll have a professional looking deck/railing that will have a better finished product by choosing redwood.
This can be a great choice for homeowners who want a deck with minimal maintenance. It will cost you about twice as much as a redwood deck, in materials and labor, but it will last a long time without any need for replacing boards.