Must I buy my uniform and equipment only from where I train?

Generally, all members should get their uniforms from their own training centers as this will ensure "uniformity".   You would also be supporting your school as the business is not solely based on membership fees.  At Ooi's TKD, most supplies will be cheaper than normal retail.  At times retail stores may be cheaper, for end of line items or promotion sales.  Difference in quality of product also may determine prices.