How should i spend $500-1k on equipment (nikon)?

I currently have a D90 with a 60mm 2.8 Af-D and my trusty tripod but thats about it. I would be interested in getting a flash and a wide lens but thats about all i have on my list. I mainly do macro/still life but i'm getting into portrait photography which is why i'm looking to buy more equipment.

Any help or suggestions is greatly appreciated

SB900 and the 35mm f/1.8
Great for portraits, wider for landscape and for getting more in than the 60mm can in a portrait.

Flash.sb-700 as an allrounder, a good macro/ring flash if you want something mainly for portraits and macro.

Wide lens. How wide is wide? A sigma 10-20 isn't bad but perhaps an 18-105 would do nicely