I'd buy a smaller sectional to start

That's a monster! Mistake you'll live with for years! Try to exchange for a 3-seat sofa and two armchairs. You'll be much happier over the long run! If you can't return it, use it in the man cave and devote the living room to much more comfortable seating for socializing. No one has a place for their arms on a sectional and no one wants the corner seat. You're already having to dismantle it; just get rid of it and move on.

First order of business is to figure out what your style is. Put in top search box various styles - casual, transitional, contemporary, etc. Notice what you like and don't like. I'd love to see you pick up the red from your pillows for your accessories. The medium blue color is pretty also. Just because something is on sale, that doesn't mean it's right for you and your space. Take your time and get items that you really like.

Maybe the pics are misleading. I currently have my chair and sofa and the sectional actually takes up slightly less space then my chair and sofa does. The sectional is purchased and finalized. There is no returning it.

Also, I’m a big fan of sectionals, which will likely spin heads on here. I have limited space and like recliners. I also like to lay down a lot and it’s hard when you have multiple people on your sofa. My space is restricted and I can only put an L-shape in my living room. If I make the L with a sofa and chair (like I have now), it doesn’t suit my needs. Like said, I do t have the sectional yet...but it fits perfectly my needs and space. I just need help with colors, pillows, and rug. Thanks!

My style tends to lean contemporary, but not too wildly contemporary. I don’t care much for the chrome and shiny look. I feel like my original look with the white sofas and white/black theme is a little cold and I’m trying to warm the area up just a tad bit. Not drastic, because I think my new taupe sectional will form a bit of a nook with a warmer color. I will be replacing the red pillows and that’s why I was considering a different color. I live near the beach in a 2nd floor condo and don’t necessarily want a coastal theme, but I’m definitely not opposed to working in blues, teals, and sandy colors. On the right side of the picture are my sliding lanai doors and that’s why I keep it open, for light and to see out at the landscaping.

Wall and sectional colors are both neutral so you can do anything with the rug, picking up the colors from it in the pillows. Do you like geometric, tribal, contemporary or any special style for the rug? A busy pattern or something more soothing? You really can't get a rug until the sectional is in place so you can measure for the right size within the constraints of both the room and the sectional. I prefer rugs slip under the front 1/3 to 1/2 of the seats and extend past the ends by at least a foot or more. You can tape that out on the floor with painter's tape once the sofa is in the room. If the measurement isn't a standard rug size, then go up to the next size if you can. Seeing the vertical blinds hints that you may be in an apartment. If you're planning to change those, let us see more of the window/slider?? configuration.

I would go first with rug, then picking color from rug for throw pillows.

Current picture..

Everything is measured. I would use a 8x10 rug. I’m keeping the vertical blinds since the sliding door is frequently used the vertical blinds are most convenient.

My floor is kind of “busy” so I have always steered towards plainer rugs.

I think you could jazz it up and do this deep maroon. works w/the pillows, and has the warmer tones in there that match the flooring.

bring in some more greenery. maybe something taller in the corner

try a diff type of chair over there too. maybe something a bit more mcm looking

I'd mount your tv to the wall and do a console that works better w/the furniture.

I love either of these w/your sofa and art.

Light floors, walls and furniture I go for a dark rug.

I’ll be replacing the rug and pillows so there’s no need to stay with a red or the Belushi canvas. I’m just looking for something a little more inviting. I’m not going to hang my TV on the wall or buy a new TV stand at this time. That’s too involved. I’ll work on the corner chair and maybe higher greenery in the future. Right now just need rug, art, pillows. Would rather keep the rug color-free so I can easier change colors in the future if I’d like. So (if I use a color) I’d like to stick to matching the art and pillows. The rug won’t be very visual anyways by the time it’s under the sofa and with the ottoman in place.

if that's the case, then just get a neutral rug you like. maybe like this textured Flat Weave

as for art, cannot possibly guide you there since it's personal. if you want color, then pick art w/color

or try painting a wall or doing something like this:

it's a neutral rug with 3 colors and a simple pattern. further color is done w/pillows and an accent chair.
if you want to stay really neutral, then follow these examples in the pics.

That's all you need