Question on the transfer process?

I’m a current student at UC Santa Barbara and I’m considering transferring for a multitude of reasons. However, I’m confused on what the entire process entails. When should I start preparing my essays, filling out applications, getting letters of rec, etc. ? I’m a freshman right now, and I would be applying during my sophomore year so I could transfer for the fall during my junior year.

I’m currently an Economics and Accounting/Actuarial Science double major at UCSB right now and I want to transfer to Columbia, UPenn, or McGill for Actuarial Science/Econ/Accounting.

I’ve heard that UCSB has a very good Econ + Accounting and Actuarial Science program, but are the programs at Columbia, McGill, or UPenn better?