What scanner is good for a beginner?

I'm still a student but want to become a diesel mechanic/technician. I have all the basic tools and a good multimeter. I know there are a few other things I need, but my question is what diagnostic tools would be good for other mechanics. I feel like truck diagnostic tools are over-advertised even though I get student discounts. This is just my opinion. What scan tool brands should I look into before I get started?