Auto Filter goes across the top of your worksheet, so all headers are
included.
Generally, you use Auto Filter to narrow your list based on criteria in one
column.  If you add a second column to your Auto Filter, then you are taking
an already filtered list and making it even smaller based on your second set
of criteria.
It sounds like you have main categories in column A that should always show,
but then subcategories in column B that you don't want to show if there's no
data for that line in column C (and this assumes you are not putting a zero
but are just leaving it blank).  If this is what you're after, then turn on
your Auto Filter for columns A:C and filter column C for NonBlanks.
If you are using zeroes in column C, then you need to set up an Advanced
Filter.  The Excel help menu can walk you through that in no time and you'd
just set it up to only show rows where the value in C is greater than zero.

I assumed your data entry was on another worksheet.  If that's the case,
then the AutoFilter will automatically hide/unhide the appropriate rows as
data is missing/added.  You can just always leave it set to show "NonBlanks"
for column C.  Just don't bother touching the filter buttons on columns A or
B.

Copy the following code:

Sub HideSomeArrows()
'hide some autofilter arrows
Dim c As Range
Dim i As Integer
i = Cells(1, 1).End(xlToRight).Column
Application.ScreenUpdating = False
For Each c In Range(Cells(1, 1), Cells(1, i))
  Select Case c.Column
' The case numbers below tell Excel which columns to show
' the Auto Filter drop down button for.  Typing 1, 2, 5 will
' only show the Auto Filter buttons for Columns A, B, and E.
' Note that every column must have a header, as this process
' stops at the first blank cell in row 1.
    Case 3
      c.AutoFilter Field:=c.Column, Visibledropdown:=True
    Case Else
      c.AutoFilter Field:=c.Column, Visibledropdown:=False
  End Select
Next
Application.ScreenUpdating = True
End Sub

On your report worksheet (I'll assume it's called Sheet2), right click the
Sheet2 tab and select "View Code".  In the dominant window that pops up,
paste this code, press the button on your toolbar that looks like a "Play"
button, and ignore any errors that may or may not pop up.

Then use your windows taskbar at the bottom of your screen to go take a peek
at your worksheet to make sure it turned off the auto filter on columns A
and B.  If it was successful, use your windows taskbar to go back to your
VBA code editor and delete the code.  We're done with it, so you don't need
to keep it in there.