i dont know your budget but you can do any of these for free

layer large cotton tablecloths (or blankets) i like this and this

glass cups, or dollar tree glass vases, use different sizes, fill them with whatever flowers, leaved tree branches, whatever you can cut from outside on the day of the party

just put a bunch of tealight candles on small plates or in glass cups all over the table

put throw pillows and throw blankets on the chairs

let me know if this helps :)