I‘ll be staying in Lee Garden Apartment. The best means of transportation to Badaling Great Wall?

You may take bus no. 877 from Deshengmen to Badaling directly.
From your hotel, you can take subway line 5 from the nearby Dengshikou Station; transfer to line 2 at Yonghegong and get off at Jishuitan; leave from Exit B2, then walk eastwards to find the bus stop of bus no. 877.

Thank you for your reply ! :)