Right now, after a successful start Steem tribes are growing. Some more than others but we can be sure about something, the Steemit engine has changed all.
I have personally experienced a great journey on Sports Talk but I know very little of other tribes. Which one is the best? what tribe is growing faster, which one has the more users? Stake?

I have several friends most of them, graphic designers, they want to start creating content, they have seen my results on Sports talk, but I don't know what's the equivalent of sports talk for designers.

I can't really recommend them Steemit cause it would take them soooooooo maaaannnyyyyyy yeeeeeeears just to make 1$ Usd (haha), but with tribes, they can invest, create content and be rewarded and start growing.

A competitive reward system that can rival MEDIUM, for example, is sports talk but, what is the equivalent for designers, photographers, and artists? I am looking for a good tribe for them to join which with a small investment they can see results, just like me.

I do think we are a community and honestly, for example, we the ones in Sports talk we can say it's a little technical and its always good to get in touch with someone that knows the numbers. If you invest Y, and post every day and get Z votes you could be getting W and enjoy also getting rewards with your Y curation yield.