Basically I'll be buying magnetic air filters so I can minimize dust intake and I want to buy the right amount. I have 7 fans at the moment and I'm not sure if they're in the right direction and/or CFM for positive pressure.
I have a case down below which isn't actually mine (I just found someone with an Antec 300 case. Blue arrows indicate air flow.
Whoever that case belongs to, sort your bloody cables out!!
airflow you have shown is 'correct', although each case will benefit from experimenting to find the best set up for your situation,
I would have the most powerful fans as front intakes with the filters you want,
and the rest as exhaust with no filters
(I don't class the Heatsink fans as intake or exhaust)
but filtering fans slows the flow so having the most powerful ones there will compensate and exhausts don't ned filtering as they are pushing out of the case
I've marked this diagram with yellow circles being fans from the power supply and graphics card. They conflict with each other so I'm not sure if I want fresh air to go into the area or to make the heat escape by making it an exhaust
I'm the resident cable management monster here sorry
if I can see cables I get upset hehe
I'll link a pic if you want to see what to aim for
have your Psu fan down as in that picture, that means the flow is from outside the case and exhausts out the rear, so it doesn't affect internal flow,
if you don't have grill in the bottom you can always cut a section out or drill holes there if you wanted to
if you have the powerful fans as intake and maybe use the fancontroller to lower the exhaust speeds, you should easily attain positive pressure,