One may not buy any garment that requires the Berakha (blessing) of Sheheheyanu from Rosh Hodesh Ab, even if one intends to wear them after Tish'ah BeAb. However, if there is a need to purchase items that do not require Sheheheyanu, such as socks and undershirts, even though it is preferable to purchase them before Rosh Hodesh, they may be purchased even after Rosh Hodesh Ab. They should not be worn, however, till after the ninth of Ab.
Non leather shoes must be worn on Tish'ah BeAb. If the only shoes that one has that do not contain leather are brand new, they may be worn for the first time on Tish'ah BeAb. Ideally, however, they should be worn for the first time on Yom Kippur.
(See Hikhoth Haggim - Maamar Mordechai, ch. 25, Oth 34 and 35)
