You can take the tourist bus No.3. The route of it is as the following:
Zoo--->;NRS--->;Taipingmen--->; Zijinshan Telpher--->;Botanical Garden --->; Mingxiaoling Mausoleum--->; Mausoleum of Dr. Sun Yet-sen--->;Linggu Temple Park
Operating hours: Initial stop 8:30- 15:45 Ending stop: 9:15- 16:30

You can either buy tickets on board or use a kind of IC card (something like a credit card used for transport). The IC cards are issued by the city transport companies and money can be added in some banks.