Dude get some leds or a stick of neon , hide the bulb under there , get the power from something on your park lights like a gauge(boost gauge in my case) so you can have the effect going all the time at night.
So lets see :
2 sticks of street glow ultra mini = $20
electrical tape - $2?
Stick them under the dash or run some small screws through them
Neatly hide the excess wires or shorten it
turn on your parks
and bam you got a $25 footwell light job.
Rinse and repeat for the backseats!
Time to install 10 mins!
Pics: from my crappy cell