Question about Cell Phones and Driving Directions

I know that actions on the GMB profile are signals. Let's say I wanted to buy some cell phones. I have an idea of what I want to accomplish. Here is what I'm wondering:

Is buying cell phone for off page seo a waste of time?

Does it matter if i buy multiple phones from the same provider or should I try to buy phone from multiple providers?

What are the cheapest cell phones/plans for what I'm looking to accomplish?

Do I /Should I create unique accounts for each phone?

Anything i should know about creating G accounts?