Now these are just my opinion.
1. Vivarium-20 Long
2. Aspen is good
3. Hides are good
4. Water bowl of course, won't live long without it
5. Personally I never put things for a ball python to climb on, they are ground dwellers so it simply isn't needed
6. Tongs are a must have
7. Snake require belly heat, so a UTH is a must.
8. Snakes do not require lighting such as lizards do, and are perfectly fine without it.
9. Food is always good.