1) I don't spend much money on my clothes. I try to buy comfortable things at a medium price. I don't have any elder brothers or sisters so I wear only my own clothes.  (или если есть старшие братья/сестры, то ответ возможен такой: Yes, I had some worn clothes from my elder brother when I was a little child.)

2) I have never bought any second-hand clothes because I want my clothes to be new.  

или

I have bought some second-hand clothes because second-hand shops often offer good clothes at low prices.

3) I don't have any tattoos because I'm too young for them, but I've got my ears pierced so I can wear earrings.

4) Traditional clothes in Russia were a long pinafore dress for women and wide trousers with a shirt for men. I don't think anybody wears them in everyday life now.

5) My grandparents prefer wearing something comfortable and I prefer wearing something fashionable.

6) There is a school uniform at my school and it's compulsory. Girls wear skirts, blouses and waistcoats, and boys must wear trousers, shirts with ties and jackets. The colours of our uniform are blue, black and white.

Sure, I wouldn't go to the party in my school uniform. If I go somewhere to chill out with my friends I'd rather choose jeans, some t-shirt and a hoody.