I want to get into car mods

Im a young man trying to get into car modding but from my perspective its kinda overwhelming. There are so much things you can do to a car that i dont really know where to start. I already have a few basics like doing my oil change, checking different fluid levels, tire pressure and other maintenance things. I have a student job that doesnt pay much but in 2 years ill have a more decent salary. i know modding can cost LOTS of money but i still wanna start somewhere. I dont have enough to buy a really modable car so for now i only have a ford focus 2011 se with auto transmission. I realy love my shitbox and honnestly i dont plan on selling it one day, its either gonna end up at the junkyard or a modded car so i can basically do whatever i want on it.