The busiest time is certainly the week between Christmas and New Year, with busyness trailing off after that as industry goes back to work. In the busiest times you can still access the multiple free public jetties and swing moorings, but it's best to occupy a spot by about 3pm. However if you have a trailer boat, then tying up to a beach is fine, common and normal. Tidal range is about 20 cm. Most popular spots to tie up are Duck/Picnic Arm, Dawson's Cove (Paynesville/Newlands Arm), and the Bunga Arm just across the sand dunes from the ocean.
The Gippsland Lakes are not next to a metropolis, thus there are multiple free (24 -48 hrs) jetties, picnic grounds with green grass, free water (BYO tap connection and hose), free rubbish, free hot showers (4 minutes of hot water), and free gas barbeques in the most popular spots and some stick barbeques as well, and toilets & pump-out spots. The water is usually algal green or slightly brown now due to rain. Free and secure public car& trailer park, or you could pay for parking somewhere (caravan park/boat storage?).
Without a hassle you can sail from Lakes Entrance town to Metung, Paynesville, Loch Sport and through the strait to the start of Lake Wellington (Plover Point) as Peter wrote, with many side arms, bays, etc. New Years eve will see fireworks mostly at Paynesville, but at other towns also. There are at least 3 rivers to navigate a good 10 - 20km (Nicholson, Tambo and Mitchell), and villages at Lakes Entrance, some small spots near Nurngurner, Metung and Chinaman & Boxes creeks, Eagle Point, Paynesville and Loch Sport. A small village at Ocean Grange, plus towns on the 3 rivers above, so you can shop/go to pub and have a free jetty.
The maps seem only online now:
gippsports.maps.arcgis.com/apps/webappviewer/index.html?id=b0359988ca3241729e331f284f44587c¢er=147.6,-37.99&level=11TrailerSailerPlace forum has lots of posts for the lakes:
trailersailerplace.com.au/phpBB3/viewtopic.php?f=2&t=17125&p=211932&hilit=Gippsland+lakes#p211932 Overall it's quite a nice place, not crowded, free jetties and swings, showers, etc. Worthwhile.