Who can I give my proxy to for an AGM that I am not able to attend? Can I give it to the Managing Agent or the Caretaker?

You have to look at the STSM Act in this regard – and specifically PMR 20(6):

PMR 20(6)        A proxy need not be a member, but must not be the managing agent or an employee of the managing agent or the body corporate

Some people say that if the Managing Agent or the Caretaker is also a member of the Body Corporate then you can give them a proxy to vote at the meeting on your behalf but this is not correct.

PS – Always also keep in mind the two proxy rule