Power up Wigglytuff if you want. It's not the optimal offensive moveset and her CP will most likely have you placed on the low end tier of gyms even if you were to power her up to level 30+. It's not a bad catch, it's really your preference since you won't really be using her to dominate offensively or defensively.
In regards to your Dratini, what's its CP at? Do you have enough candies to evolve all the way to its final form? IVs are good if you can afford the candies (and dust--depending how high you wanna push him).