If you plan to participate in the challenges on a regular basis, these are some tools and ingredients that will be helpful to have on hand. Note that this is a complete, but not exhaustive list, as there may be unique tools or ingredients needed for a specific challenge. They will be announced ahead of time if needed.

Highly recommended:
Loaf mold
Slab/tray style mold
Stick blender
Digital scale
Digital thermometer
Mixing bowls
Spoons, spatulas, whisks
Swirling tools: chopstick or bamboo skewer, hanger tool
Large kitchen knife or single wire soap cutter – wood or metal/acrylic base
Inexpensive planer – like this
Inexpensive beveler – vegetable peeler or one like this
Fine mist spray bottle with 99% isopropyl alcohol for decreasing soda ash
Freezer paper for lining wood molds
At least one decelerating, non-discoloring fragrance – see the list in the Helpful Tips section
Always wear your safety glasses and gloves!!

Definitely helpful, but not necessary:
Mini Mixer with flat disc for colorants – small battery operated or larger battery operated (electrical only available with EU or UK plug. Ebay or Aliexpress – both ship from China. Universal plug adapter.)
High Quality Planer – acrylic
High Quality Beveler – designer edge or stainless steel
Cutting Station – Hercules or Caterpillar
Lazy susan – like this
Soap dough – make your own, or purchase
Individual cavity molds – anything silicone, great for leftover soap batter!
Natural soap colorants – resources from Soapy Friends