The amount of data or mobile plan needed is unique to each customer. Unlimited plans are the most popular and are recommended as they will cover all your data needs for high, moderate and light data usage for streaming video/audio services, gaming, social media and web surfing.
Your average data usage will determine which plan is best for you.
As a general guideline, consider the following:
Light User 0-4 GB/mo
Moderate User 5-10/GB/mo
High User 11+/GB/mo