Russians tend to dress as well as their salaries will allow. Men would tend to wear either a dark suit or jacket and trousers with a tie and women mainly wear business suits or blouses and skirts.
It is important, for westerners to look smart and appear to be expensively dressed as this enhances credibility. From the safety standpoint, it is probably not advisable to wear very expensive watches or jewellery.
The winters can be extreme (as can the summers) so ensure suitable clothing to meet whatever the prevailing conditions. Be sure to remember a hat, gloves and scarf in winter.