In December 1911 after Mongolia became independent, the Qing vassal state of Tannu Uriankhai became the independent Uriankhay Republic, the Republic was quite unstable due to many Tuvans wanting to join Mongolia instead of staying independent. Fearing Chinese occupation, Tannu Tuva joined Russia as an autonomous Protectorate in April of 1914. Chaos began in Tuva in 1918 as China invaded Tuva as the Russian Civil War broke out, between 1918 and 1921 Tuva was a warzone between Soviet Union and China. In 1921 the Tuvan People's Revolutionary Party took over Tuva with support from the Red Army, the main leaders of the new Tuvan People's Republic were Mongush Nimachap & Mongush Buyan-Badyrgy. in 1925 former monk Donduk Kuular became Prime Minister of Tannu Tuva, he would improve relations with Mongolia and making Buddhism the state religion. In 1929 after 4 years of rule, Joseph Stalin would send Tuvan youths to coup Kuular and to align Tannu Tuva closer to the Soviet Union. Several short reigned leaders would go by and finally Salchak Toka would take control of Tannu Tuva in 1932. Toka would supress religion in Tuva and would drastically modernize and start to industrialize the urban city of Kyzyl.
A good strategy for Tannu Tuva is to exploit the Soviet Union for military help in China. Since they generally don't have any interest in the area, if you beat Japan to it, you can gain huge amounts of manpower, even by taking out only the warlords.
One should start by attacking Sinkiang since it is the weakest of the warlords that we are able to attack. After peacing out with them, by either annexing or puppeting, direct your attacks to Xibei San Ma as Tibet is better defended. Take out as many warlords as possible until the Marco Polo Bridge incident occurs and Japan and the United Front are at all-out war. You must attack alongside Japan, calling the Soviets, as previously stated, your communist allies won't take land away or make puppets, this includes Mongolia too. Use the tactic 'Shadow Puppeting created by FeedBackGaming on Youtube, in which you puppet China with the cheapest province, preventing Japan from creating Reorganized Nationalist China making them uninterested in all of the Chinese provinces that do not border the sea.