How much data does Simplifi use and/or what data plan should I get for my Simplifi?

This depends solely on your use case and intended usage.  Here is a rough guide:

• Failover: Less than 2 GB (depends on typical duration of mainline ISP outage)
• Travel and occasional use: 1-4 GB
• Primary Internet use individual: Depends on Use Case and/or usage
• Primary Internet use for small business: Depends on Use Case and/or usage
• Primary Internet for POS Terminal: 1-4 GB