Softwood decking is the cheapest natural wood option with a reasonable consistent grain and colour, it does however tend to contain a lot of knots.
Softwood can often seem to be appear as a very cost effective solution. However, in our experience, softwood tends to twist an warp considerable, especially if the decking is relatively thin. knots have also be a considerable cause of issues, over relatively short periods of time. Softwood boards are readily available and options also include ones with anti slip inserts added for extra grip. Boards are typically fixed down using stainless steel screws.