One approach is to cite Gareis (2010) as the source of the other citations:
According to Gareis (2010), many international students complain about a lack of meaningful contact with host nationals (cited by Gareis, 2010: Gareis, 1995; Klineberg & Hull, 1979; Marginson, Nyland, Sawir, & Forbes-Mewett, 2010; Ward & Masgoret, 2004; Yashima, Zenuk-Nishide, & Shimizu, 2004).
If you use this approach, then you need to include ALL these in your References list (a.k.a. Bibliography). In this case it would be 6 references total.
This approach is most useful if these specific sources are important for your purposes, either because they establish credibility, present details, or make important connections to lines of research or results.
Another approach is to omit the specific citations by Gareis (2010), but also to note that you omitted them.
According to Gareis (2010), many international students complain about a lack of meaningful contact with host nationals (five citations in Gareis, 2010 omitted).
This approach is most useful when you only need the main citation as support of the statement and the specific citations are not useful or necessary for your paper or for the reader. In this approach, you'd only have one entry in your reference list for Gareis (2010).