Playing RDR2 first is a bit of a mistake, you'll miss some weight to the story and one of the most powerful scenes in the epilogue only works if you know what happens to Marston and Abigail.
In general, a lot of the impact of the story comes from knowing the events of RDR1 and being able to appreciate Arthur's perspective so I'd actually advocate a reverse order for this one.
Also, the only thing RDR1 is inferior to 2 in is graphics/world detail. Nothing else. The story is just as compelling if not better overall, just not tied by Arthur's character.
If you start with 2 and become interested enough in the story, then 1 will not be a pleasant transition because of the graphics.
Having said that, I wouldn't buy 1 at that price.