Spend the money on Quality apparel. Being cold sucks and it will make the hunt unenjoyable. Make sure your toes stay dry and warm. The house of the rising gun blind has insulated walls and roof to help hold heat. A small portable heater will keep you relatively warm. Hand and feet warmers are another good alternative.
My toes get cold in the summertime. I found “Minus 33” wool socks are great for me. I love their base layer also. Make sure you have ear covering and gloves in your blind bag.
In my blind bag I carry my belly-up thermos, coffee cup, gloves, sock cap, extra batteries for the mojos, shotgun shells, and dried cherries. Never know when you’ll need a little snack. I also keep a fillet knife and 2 zip lock baggies for the harvested breasts. A small package of dude wipes are handy for many things.