What I did when I first started was sign up with every company possible. I also did every shop that came my way. This way, I discovered what shops and MSCs I liked and didn't like.
Years later, I'm still activated with all of the companies even though I work for maybe 10 on a regular basis. Also, things change. MSCs get new clients, or I do shops that I would not have done in the past.
Keep your options open.
"I told myself to quit you; but I don't listen to drunks." -Chris Stapleton