hay man, i have a 2011 s and the first thing i did when i got it was a cai. i made mine but i have heard so many good things about the fswerks cool flow intake. probably the best one you can get for the money. but like i said i made mine and it does the job just fine for only like 50 bucks:) i too have a tight budget but any extra money you can save will help out alot. iv had my car for almost 2 years and i have the intake i made, the fswerks race exhaust(highly recommended) its lowered and have nice wheels and a tune. if you want some more power and noise i would get the exhaust next after a cai. the frpp lowering setup is great for the money so i hear. im actually saving for that now bc i have eibachs and their really not all that great of a ride.
And last with the wheels, seeing as how you have the ses i would plastidip them bc they look good black and it also saves you a lot of money on wheels at this point in time