How fast is my Hot Wheels car?
Jelly, 24 bytes
“zẈ€$ụ¤’b6’ị@µỊị⁾+×żCFḊV

Takes a list of 0-indexed ingredients.
Try it online! or see a test suite
How?
Uses a slightly convoluted form of compressing the values as a base-6 number and the fact that the multiplicative entries are the negative ones. Instead of simply shifting up by 3 to get the base-6 digits, the complemented values incremented are used - this saves bytes by allowing the Ị atom to pick out the negative entries prior to the complement step while also saving a byte in the base-250 compression.
“zẈ€$ụ¤’b6’ị@µỊị⁾+×żCFḊV - Main link: 0-based ingredient list  e.g. [6,4,5]
“zẈ€$ụ¤’                 - base 250 compressed number: 120851767994004
        b6               - convert to base 6: [1,1,0,5,0,1,0,3,1,1,4,2,1,0,3,0,1,0,0]
          ’              - decrement: [0,0,-1,4,-1,0,-1,2,0,0,3,1,0,-1,2,-1,0,-1,-1]
           ị@            - index into [reversed @rguments]          [0,4,-1]
             µ           - monadic chain separation (call that x)
              Ị          - insignificant(x)? (abs(x)&lt;=1)            [1,0,1]
                ⁾+×      - ['+','×']
               ị         - index into                               ['+','×','+']
                    C    - complement(x) (1-x)                      [1,-3,2]
                   ż     - zip                                      [['+',1],['×',-3],['+',2]]
                     F   - flatten                                  ['+',1,'×',-3,'+',2]
                      Ḋ  - dequeue                                  [1,'×',-3,'+',2]
                       V - evaluate as Jelly code                   -1