Most people on this site who understand enough about magick will call you out on it, because you cannot transform yourself into any creature, real or fantasy.
You are a human and always will be. Magick is not able to change your physiology, DNA, gender, species etc, and cannot break natural laws.
Anyone who claims to have had success will be a roleplayer, these things simply don't work, most have been added to the site by those who don't understand magick as anyone in a council position of a coven is able to add a spell to the site.
The most common one is to shift into you animal spirit or into a similar form to your spirit guide, it is also the most suggested because it's easy and fast to learn, as you have already a link with your animal spirit/spirit guide/totem, etc.
The second one that i know is by making a pact/contract with a spirit that is nearby or you summoned, this is not suggested though because demons or any other malevolous entity might take the form of the animal/spirit/entity that you summoned and fool you to make a contract with them.
I personally, didn't tried neither, but my master said that the both worked for her.
I have been practicing magic for four years now and have learned that you are not really able to fully transform into something. But I believe that you are able to take some attributes of the thing that you want to transform into. Any spell make work in helping you but if you try and make your own spell it might work. I suggest you watch Akasha wolf's videos about magic and spellcasting they have helped me a lot in learning more about magic and witchcraft.
I, for one, don't think you're dumb. We all have moments of wishing we weren't who we are, what we are, or where we are (astral plane accepted)from time to time. Transformation spells do work as long as you (human as you are) have the capacity to be what you are transforming into. I other words... Think of the attributes of the animal you'd like to be more like. Maybe you need to be stronger (like a bear), fearless (like many animals), More dominant (like a tiger), etc. What is it that attracts you to being the animal in question? Focus your energy on transforming yourself into a better you with more of whatever attribute that is for you.