For all Retreat @ Home you may want to invest in a good pair of trainers or comfortable shoes for walking and a good sports bra is a life savour.
For the Express Retreat @ Home you need no equipment if you already have hand weights then you can use those to increase the intensity of the workouts.
For the Signature Retreat@Home you will want to get a set of hand weights (1.5 kg or 2 kg is fine ) and a small Kettlebell (4kg, 5kg or 6kg) to allow you to take part fully in all the daily workouts.  However, there are always adjustments offered if you don’t have the equipment so don’t worry too much.  Equipment is nice to have not a need to have.