Luggage and bags: Depending upon the time of year you travel will depend on warm or cold weather clothes. Cold weather clothes being much bulkier and heavier beware of the old fashioned and out of date (in my opinion) 20 - 25 Kg baggage allowance.
Clothing/Shoes/Weather Gear: These are not slovenly people. They are very modern, trendy and chique. If you don't want to stick out like a sore thumb or appear like a clown or a tramp, dress well at all times. Smart casual for everyday and formal (suite & tie) for theatres restaurants etc.
Toiletries and Medical Supplies: As all things are written in a language you probably won't understand, like milk being called molakov in an opaque plastic bag sometimes, takes necessary toiletries and medical supplies with you. Especially medical supplies. They can be expensive out there.
Photo Equipment: Film is cheap.
Miscellaneous: Take western chocolates if you are visiting female friends or relatives. The likes of Quality Street or Roses you wont find out there so these will be very much appreciated.