One of your first stops should be Taichung Harbor Visitor Information Center. Here, you'll be able to orient yourself and get some great tips before you begin exploring.
When you've finished up at this Wuqi District tourist information center, why not check out Gaomei Wetlands, Providence University, and Mitsui Outlet Park? They're not too far from Taichung Harbor Visitor Information Center and also a hit with tourists.