Carbon Filter help, please

so is it better to have it set up so that it is fan then filter or filter then fan? Never used one before thanks.

Does anyone know if this is any good?Activated Carbon Air Filter Grow Light Odor Scrubber - eBay (item 160210982151 end time Apr-21-08 07:31:10 PDT)
I wanna buy something tonight! Or any good ideas for a fan and filter combo under $180?Thanks

eBay Store - FOOTHILL FILTERS: CARBON SCRUBBER, UNWANTED ODORS, HYDROPONICS

maybe something in here:

https://www.rollitup.org/grow-room-design-setup/42522-carbon-scrubbers.html