Good graphing/interpreting software
Sounds like this is offline visualization not realtime display? Like you will collect data, take the SD card out of the MCU board, plug it into a PC, and do the plotting there?

There is gnuplot. It was a PITA to set up on my Mac but it's pretty cool. I have only gone at it from the side of emitting data that was formatted for plotting but I think it will eat CSV and you can tell it what to do with the columns. Definitely has a learning curve and feels a bit inscrutable but it's been a valuable tool for me here and there.

There should also be tons of graphing and plotting libraries for Ruby and Python, if you are comfortable with writing some script. I have occasionally needed to graph something and just googled and picked one at random. If you are comfortable programming and your needs are not too specialized you can probably get something drawn in a few minutes.

Definitely does not sound like the time to write your own plotting library if I am understanding correctly.