Mazda 3's come with NGK iridiums straight out of the factory, and that is what pretty much everyone gets, they work great as far as anything I know (which is next to nothing on the subject lol) but they last forever, I'm just getting new ones because they're still the stock ones and have 73k miles on them, haven't had issues with any of them.. don't want to have any issues! lol so just taking a precaution there, they're $12 a pop.
oil was easy, sucked because of this heat though, haven't done transmission oil yet though, that will be done later this week and so will the plugs which should come in tomorrow.
haven't bought the transmission oil yet, I saw a full test on like everything, I think the Mobil 1 came out to be the best over all sorts of crazy tests (independent test too, not something mobil1 or other companies did) Royal Purple came 2nd and then RedlineMT90 was like 5th or something like that, it was pretty interesting read. Doubt I can come across that test again though, it's in PDF format somewhere
