Looks like you get a ton of useless stuff in that kit..

The thermometer/hygrometers are not digital, and the non-digital ones are notorious for being very inaccurate(up to + or - 15 degrees, + or - 40% humidity)

Some people use heat lamps. I stopped altogether because it ruins humidity and I better managed my ambient room temps while providing a hot spot of 90F with a UTH.

The water dish is way smaller than what I'd give a ball python. From the looks of it, it looks like one of those ultra shallow dishes I use for my crested geckos.

As for substrate, it seems most people use coco fiber of some sort(shredded or from brick form), aspen, or newspaper. That doesn't mean douglas fir is bad, but I don't have any experience with it.

There is only one hide in that kit, and you can make your own from tupperware or other goodies for real cheap at a wal-mart.. I suggest 2 hides for BPs, especially younger ones.

Just about the only thing worthwhile there are the 20G long which you can pick up new for $50 or less, used can be as cheap as free off of craigslist.

A 20G long is not big enough IMO for a large adult BP. Smaller adult males might be alright in one but might also grow out of it.

That said, it takes a while for a young BP to outgrow a 20G long and I recommend one as a starter cage for anyone buying a BP that is a few months old.. some hatchlings available for sale might need something smaller than a 20G long but not after they've done a bit of growing. Most younger snakes that breeders will sell you are already big enough to do fine in a 20G long.