I'd start with bus routes that connect the South Side with Squirrel Hill, and one that does South Side-North Side without going through Oakland and Bloomfield. Longer term, perhaps completing the West Busway into downtown, and extending the East Busway.

I'd love a bike trail that goes along the Ohio River from downtown until Coraopolis and Sewickley. Also, protected bike infrastructure for going into the South Hills and the West End.