I'm having trouble finding a Dratini, and I know that it's 0.6% in a dragon type biome and 0.400 something percent in water biomes, but if possible, can I get any suggestions for what towns to go to that dratini's spawn at? I've heard of wyvern village, but that was just impossible for me...
It should spawn at Wyvern or near water at Smog Town; I've never managed to see a wild one also! You also need to keep in mind that you must be at least level 12 to encounter a wild Dratini.
What also helps, when you join the discord (https://discord.gg/7y3UmTF), the community will usually let you know when a dratini spawns or another rare pokemon. As inkventive said, its really rare!. Locked & moved.