You aren't going to have that much time to read extra materials during the school year. For most entering students I think the Restatements are only necessary if the teacher requires or possibly if they recommend buying them.
If your professor doesn't emphasize the Restatement then applying the code sections to a fact pattern will not do you a lot of good. Also remember that often times the Restatements are not the law in a given jurisdiction or for that matter in any jurisdiction. My Property professor refused to ever discuss the Restatement because he considers it to be a few academic types opinion of what the law should be and not what the law actulaly is.
I think the restatements are important not necessarily for your class, but more along the lines of legal analysis. Enabling you to apply the law i.e., restatements to fact situations.