Tramlaw

Hi, I’m extremely new to “modifying” any type of road vehicle. I have experience with atv’s and dirt bikes. When I bought my Impreza last Saturday I had originally thought it would be very easy to find aftermarket parts that actually were worth spending money on to replace or add on to my vehicle. So basically my question is does anyone have any recommendations/ links as to what I am able/should put inside my Impreza? I appreciate any and all feedback even if there’s nothing I can do.