Not sure about the Avalon stuff, but Essendon is pretty simple. First off put a flight plan in - makes it easier for everyone. Put WES as your outbound track if you want to go that way. You will get your outbound airways clearance from GROUND when you are taxiing (and ask for it).
Generally, the only time you will get WES outbound is if it's RWY17 or RWY26 for departures. If it's RWY35 you will get either Bolte Bridge or Station Pier outbound if you want to go south. Early turns are often asked for due to the proximity of YMML traffic. 1500 feet is the standard outbound level unless you ask/plan for something else.
Most importantly, if you are unsure of anything you are instructed to do SPEAK UP. Ask the ATC you are speaking to for more information if you don't understand or are unfamiliar. ATC are there to help and are not the police.
Pop me a PM if you have any more questions.
Showa Cho.