What is a good place to buy nice, slim fitted smart shirts in the UK that aren't too expensive?
TM Lewin & Charles Thyrwitt are you best bet i'd say (if the cut is ok for you)
How often are you supposed to rotate/change your suit? I have two suits at the moment.
Will you have client facing to do? If yes, a third might be useful
Is it more front or back/middle Office? Rules for back & middle are usually far more relaxed.
Managerial Position? a third might be useful
Specific Company dress code?
I'm still for a few weeks a non-managerial executive in an Asset & Fund Services service of a major bank. People dress quiet casually except exec level (specific Dress Code), new guys that don't want to be underdressed and Relationship Manager/Sales (Client Facing).
Personnally being really tall and thin ( 1.93 cm and 70 kg) i tend to rock a vest and a pants rather than a full suit to avoid looking like a slenderman and i'm seen as the snob/dandy of the office.
How often is the suit supposed to be cleaned/washed?
Dry Cleaning, once, maybe twice a year
When it gets two wrinkley: hang it in you bathroom when you take a hot shower, it should ease it
Thinking of buying 2 more suits and a ton of shirts. I might need to buy 10 additional shirts.
lots of shirts are indeed a plus. If the dresscode allow you, you can maybe get a few vests and some nice pants
Have a navy and dark grey suit. What colour combos go well? What colour shirts shall I purchase?
Flusser would say that it depends of you skin complexion.
Those posts from Parisian Gentleman (in french sorry) can help you:
The Power of Colours 4
The Power of Coulours 5
Next up: Ties. What colour ties should I have? What style ties?
Get a colourwheel.
There is also some rules regarding pattern, like no stripe on stripe and such
Get
Style and the Man from Alan Flusser which is the best basic guide on men clothing
Hope it helps.