Here are some non-suit options. I've been offered a professional (read: white collar, degree required, office setting) job wearing each of these combinations. I also have (off the) rack issues and typically just avoid button-downs.
A blazer (dark color and single button will probably work best), knit top (pop of color, a pattern or some sort of interest) and slacks or a knee-length skirt
Business dress- Knee length, conservative neckline, clean lines, no tacky details, neutral color of your choice. Wear with pumps and tasteful (subtle) jewelry.
Dress with blazer. If you're adding the blazer your dress can be a little less stuffy (non-neutral color or patterned). Keep it knee-length and cleavage-free. A quick note on tights: opaque black is probably your best bet.
Being confident in what you're wearing is more important than wearing a suit. If you can't feel comfortable in anything less than an actual suit, then by all means buy one, but I don't think they're necessary outside the most conservative professions (namely law and finance).
For inspiration on what's current in business attire look at White House Black Market, Ann Taylor, J Crew and Banana Republic. You can likely recreate all of the outfits listed above at your local thrift store. No luck at the thrift store? Outlet malls and TJ Maxx are your friend.