http://afe.easia.columbia.edu/main_pop/kpct/kp_qinhan.htm This page, from Columbia University, summarizes the key points of the Qin and Han Empires. The page gives context with other major marks in world history (the timeline of the Silk Road, the Roman Empire, etc.).
https://www.khanacademy.org/humanities/world-history/ancient-medieval/early-indian-empires/a/the-maurya-and-gupta-empires - This Khan Academy article gives an in-depth explanation of the differences and respective foundations of the Maurya and Gupta empires.
https://www.youtube.com/watch?v=DWyfS9kzalQ – Khan Academy video covering the beginning of Alexander the Great’s conquests of Greece and venture into Asia.