A couple things that are super easy to do:

• Mudflaps, recommend the Short ones by RokBloks https://rokblokz.com/collections/subaru-impreza-wrx-and-sti-rally-mud-flaps/products/subaru-impreza-20i-2017?variant=6611000262699
• Rain gaurds, Amazon has a great pair here https://www.amazon.com/dp/B083JLQSKJ/ref=cm_sw_r_cp_api_i_17EHC3P5V524J6JDS9EK?_encoding=UTF8&psc=1
• headlight bulb replacement (just put brighter bulbs in), switched em out with OSRAM Nightbreaker Lasers. Different trim levels might need different bulbs but there should be a table in your manual with what type is each bulb. Bought em through an online store where they had 2packs on sale, here’s a YouTube video on how to switch em https://youtu.be/A9CSUSQCUzk

I got them off Amazon. Here is the link: Smoke Black Tinted Tape-On Side... https://www.amazon.com/dp/B083JLQSKJ?ref=ppx_pop_mob_ap_share