A small green ball with spines can belong to several different cacti. Before using a golden barrel care sheet, confirm that the plant is actually the one described.
Record the ribs, spine arrangement and overall shape with clear photographs. Include a view from above and a side view. A ruler placed nearby can show scale without touching the plant.
Keep decorations out of the diagnosis
Paint, artificial flowers or decorative top dressing may obscure useful features. Do not assume a brightly coloured attachment is a natural flower or evidence of the plant's condition.
Ask the seller for the botanical name and keep it with the pot. If the answer is only 'cactus', treat the identity as unresolved rather than filling the gap with the closest attractive photograph online.
A general suitable container arrangement can support the plant while you identify it, but detailed temperature, watering and flowering advice should match the species. Two cacti sold in the same tray do not necessarily share the same growing cycle. Start with a usable identity before trying to explain every difference between them.
The RHS golden-barrel profile describes Echinocactus grusonii as ribbed, with yellowish spines. Compare more than its rounded outline, and keep the identification provisional if the features do not agree.
Related reading: Golden Barrel Cactus vs Green Ball Cactus: Key Features.