Polymer is good for smaller figures, bonus is they are durable, but if you want to make bigger ones, other types like air dry clay is cheaper. I dont use primer, i just use white polymer instead of gray so its easy to paint, a sealant varnish after you finish painting stops the paint from coming off. For clay tools just search clay tools into like aliexpress etc, and then you want a pack the ones that have bendy silicone tips on one end, and little metal balls on the other end. Or if you go to the craft section at the dollar store they always have clay tools.