How deep do I need to go into the series to do hardware acceleration for simple 2D games? I'm not ready for 3D at this point.

Day 235 is the episode where OpenGL is introduced. You can have the basics there (and in the following episodes), but basis for transforming coordinates is covered in the software renderer (day 90).
Day 360 goes 3D.
Note that Casey tried to use multiple OpenGL context then stopped that as it was not reliable (day 324).
You can use the episode guide to search for specific topics.

Thanks!