1. Start at Mandarin Oriental, check out Lobb (out of your budget, but what the hey?), then head upstairs to Mayer Shoes + A Man tailor.
2. Cross the overhead bridge to Prince's bldg, a few good tailors in there, plus Kow Hoo for shoes (also over budget, but may be worth a look). Walk outside to Berluti.
3. Head around the corner to Landmark and look around. All the bigs are in there, not many great deals though.
4. Exit on pedder side and head across des voux rd to Worldwide house (Jantzen). Pick up a few shirts here.
5. Cross the footbridge to IFC. Stop by Lane Crawford and look around. Weston is there along with a bunch of others.
6. If you still have money, take the MTR or Star Ferry from IFC to TST. You will find Seibu and others (WW Chan, Zee's and a bunch of other tailors) all in close proximity. Poke around in the Peninsula Arcade and Ocean Terminal if you are not tired yet.
If it were me, I budget $1000 for a decent suit and the rest on whatever else. Maybe order a few shirts from different places, so you can order from overseas from whichever one you like the best.
Shoes are not a great buy here, but it is a good place to look. Sometimes you can find some good one off sale prices. Sizes on RTW can be hard to find.