Short of hitchhicking your cheapest bet it to take the bus and train:
$167 total: Megabus at 7:40p from Orlando overnight to New Orleans arriving 6:15a ($15 for 5-Dec), continuing onward from New Orleans at 9:00a on Amtrak train, arriving Lake Charles 13:15p ($36 for 6-Dec). The sooner you can return the cheaper since tickets are more expensive near Christmas, "around the 20th" is vague, if you can leave on the 17th you'll save money. The Amtrak train back to New Orleans the afternoon of the 20th is $36 and the megabus overnight back to Orlando is $80.
$184 round trip: Greyhound has a direct bus Orlando to Lake Charles on Dec-5.
$274 round trip: Tornado bus company van form Orlando to Plant City, from there they have a direct bus to Lake Charles.
The prices mentioned here all require advanced booking and will go up as the departure date nears.