without making too many changes i would move the floor lamp to the left of the tv and get a good-sized table lamp for the table.I'd then play with the position of the couch and chair. Perhaps pull couch forward a foot or so and turn chair so that it forms an "L" to the couch. The corner to the right of the tv can be filled with a large tree-real or artificial.Window treatment will probably be the most expensive item. You might try dark brown sheer panels on rings so that you can pull them aside.A coffee table will make the biggest impact.

My additional comment is to stick with your color scheme. Those are the colors you like and you can make them work. You can find additional furniture on a budget by checking thrift stores. Also you can check online for your city's bulk trash pick-up schedule, then the evening before when folks put out their unwanted furniture and other items, you can recycle them instead of letting those things go into the landfill. Furniture does not need to match for a room to look great. It can be painted - or even covered with decorative paper - to look unique.

You can go with full curtains, but I have another idea. Create a cornice out of a large cardboard box. A wardrobe box would be perfect. Since your sliding door is long, you will have to piece it together, but it will work with tape. Measure the length of the blinds holder, then measure how far the front of the holder is from the wall. Google "cornice" to see what mean. Cut the box in half length-wise, then measure from the folded edge of the box to the cut edge and make it the same as the measurements of your blinds edge to the wall; cut off the rest. As for your length, you will have to extend the box by cutting it in half and filling in with extra cardboard until the length matches the length of your measurements. The front of the cornice should not be more than 12 in. long, so cut off the remaining cardboard. Now have a "box" that should slip over the blinds holder. Cover it w/decorative paper or old maps for a Tuscan feel.

Please start by forgetting about an outdated scarf over the sliding doors. Shop around, including on line, til you find some draperies you love. I'm thinking of a pattern with the colors you want, straight, floor length, hung from rings on a chunky dark rod, attached above and to the sides of the doors. That way they can be easily opened for access to the door. They will also help you get to a more finished look in here. [For Tuscan style, the usual colors are earthy mustard, rust and olive green, while your colors seem more contemporary American, at least to me.] Use the drapes and/or artwork as cues for accessories. Another chair in here might be worth considering. I hope this helps get you started. Good luck.