I would start with either market sizing or with profitability cases since they are much easier:
1) In market sizing cases I would try to understand the basic approach:
- How to structure market sizing case
- Key tools (Assumptions, Households, using personal experience, adjustments, age groups, Income split via 80/20, peak / off-peak calculations, replacement rate, using size of the area to calculate markets, calculating adjacent markets, sanity checks, etc).
- How to do math in the case interview
2) In Profitability cases, I would learn
- How to ask clarifying questions
- How to structure profitability cases
- How to work with data (Comparing with competitors, segmentation, historical data)
- How to answer the questions on creativity
- How to provide recommendations
3) Then I will switch to Market context cases (Market Entry, New product, Acquisition, etc). In addition, I would learn how:
- Structure market context questions
- How to analyze graphs and tables
4) After that I would look at other case types: Operational math problem (e.g. Should we increase the speed of an elevator or just buy a second one? How should we reduce the queues? Etc.), Cost Cutting, Valuation, Private equity due diligence, Synergies, etc.
Also, I would try to focus on the most common industries in the following priority(sorted by probability of getting a case): 1-retail and CPG; 2-airlines; 3-Telecom; 4-banking; 5-natural resources; 6-tech