It depends really. Small scale Daimyo might have armies of 10,000 soldiers or less, while Daimyo with larger domains could field many more. Oda Nobunaga marched on Kyoto with 50,000 soldiers in 1568. Toyotomi Hideyoshi fielded a coalition of 100,000 soldiers in his quest to control all of Japan. The Pro-Tokugawa coalition that fought at Sekigahara was 100,000 soldiers strong.

Ultimately, it just depends on how wealthy a given Daimyo was. Putting together an army isn't cheap, so wealthier Daimyo like Nobunaga could create larger armies. It also depended on how well a given lord collected taxes, as fighting in a campaign could be a form of labor tax. The Hojo in particular were very good at this. To quote from Japan Emerging, "Military innovations arose in the provinces, and the Daimyo engaged in new methods of mobilizing their troops. For example, the Hojo of eastern Japan were effective at mobilizing larger armies from the populations they ruled, so that forces originally a few hundred in the 1490's expanded to tends of thousands of able bodied individuals. The Hojo were most effective at surveying their lands and at linking military service to income, for their levies were directly based on the productivity of domains."