Redirect to directory after login

I cannot find the proper thread if there is one for this, so first off sorry.

Ok, here is my issue.

I have a multi site install with sub directories (main use is for a support ticket site) when a client signs up, they activate, and the activation brings them to the main site’s login (error #1) then if they login they go to the Dashboard of the Main site (error #2)

Plus if you click on Register on the support site it prompts you to sign up at the Main site, i think this is causing the issues.

How should I go about handling this?