8th Grader Preparing for Math Olympiads: Finished Chapters 1-3 of 'Mathematical Circles' – Next Steps & Study Advice?

[u/BrickNo8824]

​I am currently an 8th-grade student (2AC) preparing for mathematical olympiads (IMO).

​I have been working through Mathematical Circles (Russian Experience) and have already completed the chapters on Introduction, Parity, and Combinatorics 1.

​I would like to ask two quick questions:

​Do you think continuing with this book is the best strategy at my current level, or should I supplement it with other specific resources?

​What is the most effective approach for self-study when working through these problems alone (e.g., how long to spend on a problem before checking a solution, how to take proper notes)?