style forum and Ask Andy About Clothes, though ask andy is real quiet these days, but style doesn't change much so the information is still relevant.
Best piece of advice you'll get is to buy the nicest staples you can, and get all of them tailored. spend more, buy less, think more about each item you're purchasing.
for a business casual wardrobe you'll want..
2x navy jackets, look for more textured fabrics. 2 button notch lapel, lapels not too narrow and not too wide
4x trousers in gray, lighter shades work best, get a tapered no-break hem
2x trousers in tan, again lighter shades
10x shirts, mainly light blues and light greens, one or two white. OCBDs, Poplin, look for texture to keep your shirts from being too formal
as many fucking ties as possible, repp ties, solid textured ties, foulards, stay away from paisleys and shiny silk ties, too formal looking.
either a fucking pile of navy calf high socks, or get foppish and get a pile of variously striped socks to have some pop at your ankle.
brown oxfords, plain toe
brown bluchers, half brogue
brown chukka/desert boot
your existing wardrobe for weekends.
with the above you can rotate a ton and have a lot of variation, always have 5 shirts and 3 pants at the ready, swap between jackets every other day and drop off 3 pants, a jacket, and 5 shirts at the dry cleaner on friday.