First you need to know that BP do better in smaller enclosure and that your enclosure should grow with your BP a 30 gallons will be fine for an adult however it will likely stress a younger BP.
For glass enclosure use the rule of thumb the enclosure should be 2/3 of the length of your Ball Python.
For plastic tubs
Baby – 15 Quarts (17"L x 11 1/8"W x 6 3/8"H)
Sub Adult – 32 Quarts (23 1/2"L x 16 1/4"W x 6 3/8"H)
Adult – 41 Quarts (34 3/4"L x 16 1/2"W x 6"H)
1 good thermostat to provide proper temps and avoid over-heating
1 UTH Under tank heater to provide belly heat
1 water dish, does not have to be big enough for soaking as a healthy BP rarely soak
2 tight identical hides, with all the sides touching your BP's body (avoid log hides)
1 Thermometer/hydrometer such as thiscan be found at walmart for 12$/13$ and it will give you a reading for the temps on both sides as well as the humidity level. (Stick and dial sold in pet store are not accurate)