What clothes should i buy?

well i don't really like wearing trendy clothes that is in this year but would not be the next.I would like to invest some money (500$ my first salary!) for timeless and classic wardrobe :) (like a dark wash boot cut jean for instance)! I would like someone to help me i don't want to waste my money which in impulsive shopping! So what clothes should buy and what i must avoid? thanks!