Ölgii's market is where the town shows its everyday life. Travellers come for supplies before driving into the Altai, but it is also a good place to see Kazakh embroidery, felt goods, boots, food stalls, tools, and the mix of languages that marks western Mongolia.
It is not a curated craft market. Go with time to wander, and expect a practical, sometimes rough-edged place that is more useful than pretty.