@Dale-Arcadian 

"1. Would I put supplies and material used to create my product as cost of goods sold or as an expense?"

Neither.  The supplies and materials used to create your product are inventory (asset).  They are an expense only when sold to your customer and then recorded as COGS.

"2. With doing a reimbursement, do I put it as a check or expense?"

You can use either a Check or Expense transaction.  The Expense transaction in QBO is poorly named IMO because it can be used for transactions other than expenses, as is the case here.  Just make sure to assign the appropriate equity account to the transaction.  That works fine unless your business is something other than a sole proprietorship/single-member LLC or 100%-owned S-Corp.

"3. Should I consider this all as start up costs?"

See #1.