You've joined the right forum ! Lol if you don't mind used parts, the for sale section on this thread is amazing. I hear LTMW is amazing as custom work if you're willing to spend a pretty penny. Somethings can be DIY projects that'll make your car look just that much nicer (such as black grills whether gloss or matte shine, getting air scoops and painting them a custom color, and performance mods such as charcoal delete on the stock airbox with a drop in filter from k&n or afe, and clutch deay valve [if you are manual that is], and many more.)
Here's a little list of a few local SoCal shops:
LTMW in El Monte (customization master hands down! Builds everything from race cars to show cars! Full service shop. The owner can get any part you want, if he can't, he'll make it himself! The ultimate customization shop. Everything from oil changes to retrofitting and custom bumper making.)
Mod bargains in La Habra (sells parts mostly. I haven't seen any race builds from them)
Gsr Autosport in Lakeforest (sells parts but mostly a race shop with many race builds. The owner mike essa competed in formula with the bmw 350r and currently is using the bmw z4)
EAS (european auto source) in anaheim (full service shop as well like ltmw. Sells parts and even has a dyno in house to test how much power your car is whipping out as well as corner balancing for coilovers with dampering adjustments. Builds many race cars as well as some show cars.)
There are many more but these are all that come to mind at the moment. I believe all of these shops host meets and bbqs a few times a year also so come out to a few and get into the scene more and figure out what new mods you might want and a few you might not want.
Keep checking around the forums, the workers of these shops are always around the forums to answer questions and take orders from members/ customers.
BTW, Welcome to the mod life! Please keep all currency outside of wallet at all times and enjoy!
lol