Do you mean that you're a member, but you didn't apply for a ranch brand? MCBA doesn't classify its members into breeders or pet owners.
At most shows, you can show a chin whether you're a member or not. Different chapters may have different rules about entry fees though, for example I believe the NY/NE chapter will be charging slightly more per chin if you are not a member. The only show you have to be a member to show at is Nationals. However, again, it doesn't matter whether you're a breeder or not, just so long as you're a member.
Registering a ranch brand though is a good idea if you want to show your kits since you have to list each animal's number on the registration form. You could just put Z1, Z2 or even a name down, but having the ranch brand in front of it lets others know they were definitely bred by you and not someone else. Registering is only $5 and will last a lifetime. If you have a brand with another organization (ECBC or NCBC), you don't even have to pay the $5, just let Julie know.
The form to register your ranch brand used to be on the MCBA website but it's not there now, otherwise I would have linked to it. Maybe Brenda can send you one.