Now that I gots ma car...

As you must see I'm spamming all the forums for help lol.
What can I add that will cost me little money but will improve my performance by a bit.
Like will and K&N air filter, better spark plugs for example give me better performance? I don't mean 10-20 hp or anything like that, but even just a bit.
Because I don't know what kind of care the previous owner took care of it, so I'm thinking that if I put new and better stuff it'll give me a bit better performance.
Oh and cold air, which isn't that expensive, but is it any good just for a bit of boost?
I mean something that'll like cost me 200 bucks can total.
I have NOTHING left right now so this will even wait a bit!