For standard street brakes, I prefer Autozone duralast branded lifetime brakes, but I found Advance Auto Wearever to be good too. The lifetime warranty for wearout is impressive and saved me a lot over 20 yrs. Their better line of rotors at both places are good. Just don't get the cheapest ones because the metallurgy is inferior. The cheapest one's rust terribly and get hot sports from hard braking heat. The hot spots soon lead to surface cracks or warpage that requires replacement. I've had rotors crack in half. The semi-metallic premuims are probably a little better for hard braking than the ceramics, but they will wear rotors more and produce more dust. Believe me, I have some experience with brakes after going thru hundreds of sets of various brands on street and track.
For plugs on normally aspirated, I prefer Autolite or Motorcraft iridium or full platinums because they last 100k mi. However they drop electrodes quick in racing apps, even N/A. The Denso iridium is good too. I surely wouldn't be running short-lived copper plugs on a daily driver that does not see much severe duty use. Copper plugs belong in lawn mowers, race cars and forced induction apps.
For suspension, I would stick with Ford Motorsport for factory lifecycle and bang for buck. You can pay a lot more for equivalent lifespan in another brand. I haven't researched other good brands specific to the Focus, but bilstein and koni are good if they cover your application. I like Koni's lifetime warranty for street racing apps....they honor it!!
For calibration-sensitive parts like O2 sensors, EGR and such, stick with Ford OEM to avoid issues. The aftermarket is a potshoot except for specific instances where the community of experts knows otherwise and provides consistent recommendation for a particular part#. The OEM easily specifies a dozen diferent part#'s with tiny differences where the aftermarket offers just one with a "compromise" calibration that can lead to issues that are tough to troubleshoot like surging, bad gas mileage, hard start, rough idle etc.