design 101
Cosy Is a Lighting Decision
Cosy usually gets treated as a shopping problem, solved with another cushion and a second throw. It is mostly a lighting problem. Overhead light flattens a room and throws hard shadows, while warm light placed low makes the same room feel gathered in.
Turn off the big light and switch on two or three small lamps instead, at or below eye level when you are seated. Put them where you actually sit: a table lamp on a side table, a floor lamp by the sofa. Choose warm white bulbs, because cooler ones undo the effect.
Add texture once the light is right: wool, linen or a rug with some weight to it. Warm and low first, soft second. The order matters more than the budget.