So pretty much as the title says, i'm seeing it's on sale through steam the substance indie pack which includes Substance Painter, Substance designer 5 indie, and bitmap2material 3. And i have no experience with those products but i was planning on getting just the Substance Painter, but if they are all on sale i'm…
Take the whole indie pack. Every penny is well spent. B2M and Designer are extremely useful for creating new substance materials to use them in Painter.
Yes, if you want to learn to work with procedural material creation, substance designer is worth every penny and is a very relevant skill to have for artist in the game industry. Loads of tutorials and guides exist for designer as well, so that'll truncate the learning curve quite a bit.