Hello Scott!
I’m glad to hear that your avocado is coming along well! I would suggest that you transfer it into a pot with some quality organic potting soil and mix a bit of sand in with it to give it a little extra drainage. That will help to prevent root rot which seems to be a common problem with avocado trees.
I have also seen a few resources that suggest not to fertilize for the first year, but if you would like to give it some fertilizer before then, add a bit of Dr. Earth Fruit Tree Fertilizer if it seems to be lacking. Remember to get a good watering schedule down so as to avoid any problems and ensure that your tree will flourish.
I hope this helps!