I'm trying to get my horses leveled up but I'm having a hard time understanding the process:)

Since I stared this game my horses have been career horse. I'm now trying them in shows and halter class.

Do your horse level up in career jobs?

Whats the average amount of time it takes to take a horse to level 50?

What are the benefits of tack? 

It doesn't really say anything in the description when you buy it.

Thanks for any info, advice or tips:)