I either used flax meal or gluten free bread crumbs if I put anything in at all. I can't use egg so I sometimes mix some flax meal and water to make an egg replacer paste and that works well - "beefs" up the flavour too! I use lots of fresh herbs as well.I usually use beef and pork for my meatballs and I usually grind it myself. I also make turkey pork meatballs sometimes but it has to be turkey thigh meat as I find the breast meat too dry.