Funny, when I started bonsai in my first year, I also grew an avocado.
Then I started reading up. The leaves of avocado do not reduce much in sice (I got them to grow to less then 5 cm at one point) and the do not reliably grow side branches on the places you need them (So you will not get ramnification).
For a succesfull avocado bonsai, you are looking at trunks of about 25+ cm thick. To a VERY large (1 metre tall) bonsai. So yeah, it CAN be done. You will need to plant this in the garden, and let it grow untill it is about 15cm thick. Then cut it down to the first tryunk segment. Say, 30cm tall. Let it grow again, till the new grow reaches maybe 10cm thick. Cut back to 40 cm. Let it grow again till you have 5 cm leader. Cut back again to 45cm. Then start working on branches.
My guess is that you will need about 40 years to get to the point where you can start thinking about a container.
In summary: Not very suitable for bonsai.