Several changes needed, in addition to making sure that your fields are correctly formatted (Text/Category/Integer/Dec).

YOY change% =
IF([LY Spend]>0,
([TY Spend]-[LY Spend])/[LY Spend],
null)

For all formulas where field you're dividing with might be empty (null) or contain zero value, please use IF condition.

RANK([TY Spend], [TY Spend], SUBSET([Masterbrand]))

I assumed here you wish to group Spend by Masterbrand, but you can customise this format, also consider ranking Subsetsum of a field.

[Top 10]=
IF([Rank]<=10,
[TY Spend],
"0")
Again here you can use SubsetSum instead of [TY Spend].
The problem with your formula was that it was placing category value and was effectively a text field, so you could not use it for visualisation e.g. size by this field.

Now you can tick the option not to display zero values, as this formula will create zeros for those records outside of Top10.