You'll want to go for a coffee table that moonlights as storage. Crate & Barrel has a great selection of storage ottomans which will do the trick, including the Stow Leather Storage Ottoman which flips to reveal a traytop. Pair that with a super comfortable loveseat or small couch, perhaps a sleeper for guests, and throw in an armchair or some poufs and you'll be good to go on seating. If you can afford it, mount a flat screen TV on the wall. If not, and you do want one prop your regular TV on a small dresser that can store your belongings. Or, put it onto a sideboard with wheels that you can roll into your closet when not in use.
Then, think about getting a simple table, like the West Elm Parsons Desk which can be used as a dining table, a desk, a craft table, and even a side table. Add some Bamboo Folding Chairs, which can be slid under the bed if necessary. Or you might even consider a dining table that folds into a briefcase!
I hope that helps! Feel free to ask more questions, if need be. And anyone else who has lived in a studio, please chime in with advice.