I can’t find evidence of whether the support was militaristic or logistical
Between the years of 1921-1927 the Soviet Union was heavily involved in the establishment of the Whampoa Military Academy by sending a plethora of advisors and instructors to train officers within the KMT-CCP alliance. If I recall correctly the KMT was built on organizational structures by Mikhail Borodin well into the late 80s. Though I am not entirely sure about the logistical assistance during this era provided to either the CCP or the KMT, the Soviet Union offered quite a lot of militaristic instruction as well as brokerage for the temporary peace between the CCP and KMT.
As we know, the 1927 purges post Northern Expedition completely broke down Chinese-Russian diplomacy until the 1937 Marco Polo Bridge incident. Through World War II the Soviet Union provided more than 1,000 planes, a handful of tanks, 10,000+ machine guns, and around 1,000 trucks to the Chinese along with ammunition and bombs between 1937-1945.
Incidentally the aid the Soviet Union gave post-1927 focused mainly on the then-devastated CCP but by 1937 its material and strategic aid efforts were focused on the KMT out of convenience of a mutual enemy (the Japanese). Militarily the Soviets aided the Chinese with assisted airpower as well as munitions during the war. By the end of WWII the Soviet Union's equipment oddly ended up both in Taiwan and in the hands of CCP. Much to the dismay of the KMT the Soviets also sprinkled seeds of discord amongst the Uyghur and Mongolian population during and after the Second Sino-Japanese War, massively aiding the CCP.
For what it's worth the Soviet Union sent both material and personnel to China but in hindsight much of the aid changed depending on the political situation at the time in China. I wouldn't say that the aid was insubstantial, but it's telling that part of the Sino-Soviet split between the CCP and the USSR occurred thanks to what the Chinese perceived as lackluster support for industrialization and mobilization from the Soviets themselves.