Actually, it may be a good idea to stay off LSAT material. It has many different types of questions which are irrelevant as far as GMAT goes. Only once you have exhausted all other material and are absolutely in line with all concepts should you touch it if you want to practice more.
Focus more on your strategies than on plain practice.
For CR - Learn how to handle different types of questions, what to focus on etc
For SC - Learn the most common error types e.g. Modifier errors, Pronoun errors, Subject Verb agreement etc and how GMAT questions you on these.
For RC - Work out a strategy that works best for you. Things to keep in mind while reading the passage - the structure, the tone etc.
Once you have identified what works best for you, practice it on any and every question you get your hands on.
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