Where do I report Scentsy Income at $100?

It depends.   A business can claim expenses where a hobby can't. Not knowing what you spent and when you started, I can only give you the rules. If you choose business, self-employment tax is not imposed until your income reaches $400. What is the self-employment tax?

Take a look at  Earning side income: Is it a hobby or a business? which lists 9 factors after stating that a hobby is for recreation, not for profit:

• Whether the activity is carried out in a businesslike manner and the taxpayer maintains complete and accurate books and records.
• Whether the time and effort the taxpayer puts into the activity show they intend to make it profitable.
• Whether they depend on income from the activity for their livelihood.
• Whether any losses are due to circumstances beyond the taxpayer's control or are normal for the startup phase of their type of business.
• Whether they change methods of operation to improve profitability.
• Whether the taxpayer and their advisors have the knowledge needed to carry out the activity as a successful business.
• Whether the taxpayer was successful in making a profit in similar activities in the past.
• Whether the activity makes a profit in some years and how much profit it makes.