New member wanting to share and learn.
 

I just purchased A 2014 Mazda 3 GT 2.5 I'm planning on doing just A few modification to it.
I would love to help or share ideals.

Welcome to the site and congrats on the new car.

You will see your largest gains from changing how you drive, so be sure to check out: 100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com

Mod can help too, but to a lesser extent unless you're willing to really go wild (which I assume you aren't because its a brand new car). Still, you can check out our mods list here: 65+ Vehicle modifications for better fuel economy - EcoModder.com

I would recommend starting by airing up your tires to max sidewall, or somewhere between the mfg suggested pressure and it. Then I would probably work on a partial grill block for aerodynamics and faster warm up. Of course instrumentation like a SG or UG really helps too.

welcome!
raise the tire pressure to 40-44psi.
get a scangauge (see link in sig)