So thanks to Teor and Nick's help, my python client (tor OP) is finally able to successfully establish a three-hop circuit with any TOR relays in the whole public network! 

Now It's on to the Data Cells...

As of writing this, I can send and receive the proper RELAY_BEGIN and RELAY_CONNECTED to and from my exit node, but I'm not quite sure what to do next...

Do I just start sending RELAY_DATA cells (where the "data" of the cell is literally the encoded HTTP requests)?

I've tried connecting to 'www.facebook.com:443'  with the RELAY_BEGIN cells as a test (I do get a Relay Connected Cell so at least I know that part works).

After getting back the RELAY_CONNECTED cell, I send a RELAY_DATA cell with the data of the cell being the following 'utf-8' encoded string:

What I get back is a short couple of bytes:

I had no idea what this meant but after digging around a bit I found that this seems to be some part of the TLS handshake that is used in HTTPS.

So now two questions arise:

1. Is this a good TLS response? What does it mean exactly? 

2. Generally speaking, is this how the RELAY_DATA cells are supposed to be sent and received? 

Just to clarify it would be great if I could get an exact example of how the stream of data should look. For example, if someone could maybe break down the steps of how a basic HTTP GET request would work through a TOR circuit (starting from sending a RELAY_BEGIN cell) that would help me tremendously.  

Thanks again to everyone who've helped me so far, and thanks in advance to anyone with an answer to any of my questions!

Regards,

Eli