I am showing some mantelpieces too as the elements could be the same. Leaves, pumpkins and other small gourds (buy fake ones and you can use them over and over again. Falls colors in candles, use fall colors in tablecloths, napkins, and china. Start collecting "display" type items that can be used over and over again.
For Thanksgiving, I've seen some really pretty centerpiece decorations made with a straw cornucopia, filled with colorful silk leaves and faux fruit, or perhaps real gourds. I also have a cute straw turkey, left over from a gift floral arrangement, that I fill with craft-store finds with a fall theme (flowers, silk leaves, little pumpkins, etc.), or I put a glass dish in it and fill that with beautiful candies or treats.
There are some beautiful fall tablescapes out there. Try searching on Pinterest and you will find a lot! Have fun!
Here is one idea I put on my built in hutch, but it would look great on the table too.