You don't have to find complete sets of table and chairs at yard sales or flea markets. You can have a great set of garden furniture by finding a secondhand table and complimentary, but different chairs. You can have four chairs that are basically cane bottomed, all with different backs and they will be fine. Having them the same approximate height does help. You can add colorful chair pads to them if the bottoms are different and nobody will ever notice.For a lovely garden dinner table setting, you can also use complimentary patterns of white dinnerware. As long as they are all white, you can mix or match the subtle patterns for some variety.
To add some spice to your garden table, use another flea market or garage sale find such as a small, old birdcage preferably made of metal. You can spraypaint it (after washing it of course) with some pretty color that compliments your seat pads maybe. Put six small votive cups, or four is six is too many for the birdcage, and light the candles inside.