Typically two denominations, with an apporoximate 80%-20% to 90%-10% breakdown, and between 80-160 total chips in play (i consider 120 total chips as the 'sweet spot' once three-handed).
For T25- and T100-base sets, T1000s color-up the T25/T100 chips, and T5000s color-up the T500 chips. Unless the stacks are huge (or there are many tables), T25k chips are not required (and generally only 2-5 chips are needed even then).