If you're wondering whether to do it yourself or get a guide I'd 100% recommend getting one, some of the best sites are quite far out of the city, and the history is best explained by Lilly. (This is coming from someone who speaks and reads basic Chinese!) We had a two day flexible private tour with Lilly, who is from Xian herself and she was absolutely outstanding. Chinese history is long and complicated, but everything was easily explained and made sense. We went to the terracotta museum but also another tomb called hang yang ling where there were no crowds whatsoever and an even better preserved mini army. On the second day we went to Hua Shan, which was a stunning hike with spectacular view. We couldn't get tickets to the west peak because of high winds on the top, but had a fantastic climb and hike from the north peak) During our time in Xian also did a day by ourselves and it was nowhere near as good as the two days with Lilly. Lilly's English is exceptional, et en plus, elle parle aussi couramment français!