travelling to buy goods

If you have a regular supplier in PRC, you can apply for a business M type.
If not, you can apply for a tourist L type and then enter PRC for the purchase.
The basic documents for M and L type are the same, including your passport and copy of its data page, the application form attached with a recently-taken bareheaded color photo. For M type, an invitation letter from your trade partner in PRC is necessary; for L type, round trip air tickets and hotel reservation are required.