Minimum 2 pairs of jeans. One with a brownish stitch and the wash is blue but fades to a brownish color and one that stays more with shades of indigo and the stitch is blue or white or something in that family. You could add in a pair of black jeans if you wear black often. If you have the store Buckle where you live that is a good store for trendy jeans , I still like Guess for men also. If you like a more basic or traditional jean then Calvin Klein or even Gap or Levi’s.
One pair each of the following color trousers, khaki, navy, taupe/grey, and army green if you wear green, a lot of American men don’t.
If you tend to be more conservative buy 2 polo style shirts, 2 long sleeve woven shirts and 2 short sleeve wovens, and two t-shirts. If you live in a northern climate add 2 sweaters and 2 turtle necks. The turtle neck can be worn alone, with the sweaters or under a woven ling-sleeve shirt. If you are less conservative you may just ditch the polo style shirts.
3 new pairs of shoes. Brown, black, and a half boot for the coming winter in the color that makes most sense with the majority of your wardrobe.
I see some people mentioned a watch. A new watch is nice, but the rest of your look is more important in my opinion.
The personal shopper someone suggested above is a good idea. But if you enjoy the shopping part of shopping you may want to not do it. Personal shoppers usually pull a lot of garments for you so it is all ready for you to try on. If you want to be able to shop the store, talk to the personal shopper before your appointment and ask them how they usually work. If they walk the department with you, or if they have everything ready in a dressing room when you arrive.