i strongly urge you to look at fit pics from members "Easye", "Spoopoker" and "Gmmcl" - three of the best dressers on here, and they do it on a fairly slim budget by SF standards. so if you are looking to get started, and on the right path, they know what they are doing.
my personal style advice for an interview at a workplace where suits are not the norm? your personal grooming speaks volumes, clip your nails, get a fresh haircut, any facial hair should be tidy. to the point of no stray eyebrow hairs, nasal hairs,etc - a nail buffer, and tooth whitening help also.
you will want to be immaculately groomed, leaving no visual distractions. so your posture, and ability to communicate will be commanding the attention.
what to wear if not a "Suit" , - it's really hard to fail at wearing tweed. in colder weather, brown cords and a tweed with brown shoes will come across as well put together, but not trying too hard. like i said, check out the above mentioned members fits. and groom as described. also, in your briefcase or bag,-carry breath mints, eye drops,and tissues. -And don't go too heavy on the cologne.