Looking for recommended approach to storing history data locally

[itorres008]

Hello.
Old-timey programmer here. Haven't worked with JSON, but presume I can figure out deserialization on my own.
I am visualizing an app to hold summoner match history data and provide some stats.
I presume I should incrementally store data locally as requested over time. (less data to ask from API, data available probably limited to a certain time period)
As people progressively get data in JSON format, do they merge and keep it as JSON or import data into a relational database?
I'm more comfortable working with relational databases and tools and presume would be more efficient.
Thanks.