Phyllanthus mirabilis needs 0.8 cups of water every 9 days when it doesn't get direct sunlight and is potted in a 5.0" pot.
A plant's growing potential is determined from its location, the time of year, and current local weather.
Because of its swollen stem, you won't need a highly water-retentive potting mix and instead should opt for a grit or sand-based soil. We'd recommend a 'Cactus & Succulent' labelled potting mix, as it has a good blend of compost, perlite (to help airflow), grit and sand.
Chose between using a decorative pot with drainage holes (like terracotta, ceramic, etc.) or through a plastic nursery pot with an additional decorative pot. We'd recommend using terracotta as it'll absorb moisture and provide a more aesthetically-pleasing contrast to the woody caudex and foliage, but others are just as good.