Building a home gym? Costco’s exercise equipment deals make it possible without emptying your wallet. From treadmills to dumbbells, here are the top picks members are raving about right now. The Centr 2 by Inspire FTX Functional Trainer with Folding Bench ($1,399.99) is the undisputed champion with over 3,174 reviews. It replaces an entire gym with cable crossovers, a Smith…