As the bros say, the KCR (train system) is excellent, and links Fanling to Sheung Shui and Tai Po - both are small enough for you to walk around with a printout from Google Maps. Reports are mixed, both good and bad, which means you can find real gems if you knock on more than one door.
And going from there to Shatin is fast - maybe 15 minutes - there are some HGs there, which is a relatively new development, so they'll appreciate your support
And all the way into Mong Kok or TST is more like 30 minutes, Wanchai another 10 minutes or so, still not exactly a barrier to your ambitions
Even if you stay out late in Wanchai and miss the last train home, you can either
party through the night (the first train will be around 5am),
stay all night at Hourly hotel for HK$450 or so after midnight (about the same as drinking all night), or
a taxi back to Fanling is probably going to set you back around HK$300
also not a killer if you're dropping $1k on a punt ...