For learning perspective, the most entertaining class I know about is by Marshall Vandruff. I’ve studied with him a bit and he’s a masterful teacher.
If that doesn’t resonate, I’d jump into 3D! Playing with SketchUp and ZBrush/Sculptris has helped me a lot to get a more intuitive sense of perspective.
Also helpful: Autodesk Sketchbook has a perspective guide tool that is simple but very powerful.
Once you know a few basic rules, you can do a LOT with this and it’s (arguably) more fun than working with a massive sheet of paper and a set of rulers.
The perspective tool requires a pro subscription but it’s around 30$/year which seems reasonable.