Most listings are in the $20's per square foot per year. The Gilbert submarket is going through a decline in rates. In the last 3 months, the median rate fell $3 per sqft per year. That's a 11% decline in rent.
Compared to the rest of the Phoenix Metropolitan Area market, the Gilbert submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 40 listings have been made available, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. About 5% of the office spaces in the Gilbert are subleases, so you will probably have to focus your search on direct office leases. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,480 sqft. Most properties in this region are approximately 2 floors. Most buildings in this area were built in 2006 and are Class B.