Wow. That's a very open-ended question. What do you start with or are you starting from scratch? I can only imagine what my closet would look like right now If I had that much to spend. I know I would have upgraded my shoes and added a third suit.
I guess I am thinking about starting from scratch. I thought this would be an interesting topic. Off the top of my head, I think I would by a pair of nice dark brown and a pair of black shoes around $250 x 2. Should be able to grab three pair of wool pants for around $100 (Black, Charcoal, Grey). 5 shirts at $50. One $450 blue suit.
I did Joe's $1500 wardrobe and bought many of the exact items he suggests, incorporated several of the things I already had, and adapted to what I could find in the stores near me. Save for buying 2 Indochino suits, I liked buying in-store to check the fit and try to talk myself out of it.
Oh, and pitched all the other clothes! Down to about 2 feet of clothes on the rail in my closet that are more useful than the stuffed closet I had before!
Granted, I already own brown dress shoes, a grey suit, and a navy suit. However, all three are absolute musts (for me) so if I were starting from scratch with $1500 I'd find a way to include those into the budget. Knowing what I spent on them originally, that costed me $650. So that brings the total up to $1250 - leaving $250 to play with.
If you can get away with just one suit, keep the grey. I paid $350 for my navy suit so that would increase the working budget back up to $600.
I don't know what really great jeans cost anymore since I haven't bought any in 3 years, but the last pair of great jeans I bought was from Armani Exchange (don't laugh) and they costed me $50 on sale and they're still working for me.
So that leaves $550. That's like mad money in my mind since the essentails (at least for me) have been covered. I'd buy a couple pairs of chinos, but the bases are covered. Maybe get some fun socks. Maybe upgrade some of the other stuff stuff from the list. Or just maybe you can spring for that navy suit after all. :-)
Oh, and save some of the budget for tailoring. How much you'll need will depend on how much work you need done.