Phase 1: little stand alone potty. You don’t want the scarceness of a big potty and the extra effort to get up there to be a barrier. Also, then your toilet is still free for your own use.

Phase 2: IKEA stepstool + seat that goes on the big potty Potty Training Seat for Boys And Girls, Fits Round & Oval Toilets, Non-Slip with Splash Guard, Includes Free Storage Hook - Jool Baby https://www.amazon.com/dp/B079TBSK6T?ref_=cm_sw_r_apin_dp_0Y9MX4F07EANEDDDJC0W