Recommended Team: Sonic (Leader) & Tails (Partner)
Begin by dashing right, collecting rings and defeating the first few enemies. You'll encounter several loops and springs; use them to maintain speed. When you reach the first set of high platforms, use Tails' Tag Action (L button) to fly up and grab the extra rings. There's a hidden path above the first large loop that leads to a small cache of rings and a power-up. To access it, jump off the top of the loop and use Tails' flight.
Continue through the urban landscape, using grind rails to cover long distances quickly. Keep an eye out for enemies on these rails, as they can knock you off. Near the end of the act, you'll come across a series of moving platforms. Time your jumps carefully to avoid falling into the gaps. There's a Special Spring hidden behind a destructible wall near the end of the act; use a Spin Dash or a powerful attack to break it open. This act is primarily about getting comfortable with the controls and the tag-team system, so don't be afraid to explore.