Airflow should be front to back; bottom to top.
The top-front space should be left empty, because:
-As exhaust, it would pull some cool air up and out of the case before it got to the cpu cooler
-As intake, it would recirculate some of the warm air already exhausted from the case
Bottom and side intakes, both 120mm, but your case does not appear to have fan filters for either of these positions, so you'll also have to invest in 2x 120mm fan filters.
PCPartPicker Part List
Case Fan: Corsair SP120 57.24 CFM 120 mm Fans ($28.00 @ Austin Computers)
Total: $28.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-09-14 18:26 AEST+1000
Add a couple of fan filters such as these:
https://www.newegg.com/p/N82E16811999234
The stock fans that are included with cases are usually mediocre, but it's completely optional if you want to replace them.
PCPartPicker Part List
Case Fan: Cooler Master Megaflow 110 CFM 200 mm Fan ($34.09 @ Amazon Australia)
Case Fan: Corsair SP120 57.24 CFM 120 mm Fans ($28.00 @ Austin Computers)
Case Fan: Corsair SP120 57.24 CFM 120 mm Fans ($28.00 @ Austin Computers)
Total: $90.09
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-09-14 18:41 AEST+1000