my personal opinion ... (that wont really affected the warranty)

important
1) Tinted (better put in security tint nowaday)
2) ultra racing bars (strut & anti roll)
3) k&n filter
4) pedal auto lock (if u install at GS)
5) Upsize Rotor

other
6) DRL (if u install at GS)
7) 3rd brake light LED
8) Upsize sport rims
9) door step LED
if u install throttle control .... for sure will void the warranty if they wan argue

ultra racing 2 bars tat i install is about rm600 i guess ..

if u interested on bars .. u might can join our fb group... some just removed and wanted to sell .... ( lowered cars .... better dun install side bars)

upsize VTTR rotor last time GB is about 16++ ... now i think is 17++

Take a look at GTA Car Kit for mazda 3, i'm sure there is similar product at our local accessories shops.
GTA Car Kit installation