"Totally Legit", when used with air-quotes or equivalent, means "Not at all legitimate". For something to be "Totally Legit" it must be an exact copy or accurate facsimile of the original thing, however it is of irreputable origin. Also applies to stolen items and shady business transactions.
The literal meaning is obscured with subtle sarcasm. This is often used to convince friends to try something really stupid or get people to buy things.
"For Sale: Used Laptops. "Totally Legit" Windows 7 pre-installed. $200"
Fool: "Check out these bitchin' new Adidas kicks! I got them for $35! The salesman said they were Totally Legit too!"
You: "That says Adidos. With an 'o'. Adidos. Nice."
Fool: "Wha??? FFFFFFFFFFFUUUUUUUUU..."
You: "Hey, there's that van that says "Free Candy"! Once, I climbed in the back and it was FULL of gobstoppers! (lie) You should totally check it out!"
Fool: "Are you sure? Looks kinda shady to me."
You: "Oh don't worry, it's "Totally Legit"!"
Fool: "Oh, well OK, I'll try it then..." <Gets abducted>
You: HA LOL