Hello,Mr.Lucas
I suggest Badaling Great Wall for the first timer. As out of the different Great Wall sections in Beijing, Badaling is the most famous with easy transportation. The whole trip takes 5 to 6 hours.
There are two options for the transportation:
1.Take subway and train. First get to Xisi subway station of line 4 (100m west of Hanting Express Beihai Park Branch), take line 4 from Xisi to Xizhimen, get out of Exit A and walk north to Beijing North Railway Station for S2 to Badaling. After you alight, take a 15mins walk before you reach Badaling entrance.
2.Head west from Hanting Express, walk north at the cross and then take 409/83 at Xisi Road Crossing to Deshengmen. Take 919 directly to Badaling.

Thanks a lot for your answer Mr.Nicolas! We had a great time at Badaling Great Wall despite crowds of people.