Does anything like Sprite Candy and/or Particle Candy exist for BlitzMax?
Sprite Candy doesn't exist for BlitzMax.
I've taken a look at Sprite Candy and it looks AMAZING! It seems to have every kind of feature that I could want but it seems like it's only for Blitz3D
Yep, it is very good and only for B3D.
Should I have purchased Blitz3D instead of BlitzMax?
Depends what you want to do.
The benefits of Bmax is OOP. X-Platform and ships with source code (plus more).
The benefits of B3D is you get 3D and can use the add-ons created for it (plus more)
I'm now wondering that even more because I'm thinking about creating a multiplayer 3D game...
Ahhh... for Windows only I would have used B3D unless you want to investigate 3rd party 3D engines for Bmax.