OP - after getting down the basics, I shot for buying 1 or 2 suits per year. When I first started wearing suits I went for a 5suit rotation - navy solid, charcoal solid, medium grey, navy pinstripe, brown (I iiked it a la Ronald Reagan, sue me). Then for my 1 or 2 per year I'd add something different in design (like a glen plaid) or fabric (summer suit, winter suit). Don't forget a few sport coats if you are allowed to wear them on Fridays.
This is excellent advice. Maybe minus the brown suit and replace it with a charcoal pinstripe, or perhaps a tuxedo if you feel like you'll need a formal option (weddings or whatever).