Most listings are in the $20's per square foot per year. The Gilbert submarket is going through a a rise in rates. In the last 3 months, the median rate increased $3 per sqft per year. That's a 15% increase in rent.
Compared to the rest of the Phoenix Metropolitan Area market, the Gilbert region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 66 listings have been posted online, so you'll want to check back regularly for new listings. About 2% of the available leases in the Gilbert are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,120 sqft. Most buildings in this region are approximately 1 stories. Most buildings in this market were built in 2006 and are Class B.