If you want to earn a few satoshi on freebitco.in, first stop playing Hi Lo game, who will most probably make you lose the satoshi you've earned elsewhere.
True, site has pretty big house edge.
Then collect every hour
50 satoshi, unless you win last to rewards from faucet it is pretty much waste of time.
promote your referral link
Which is very hard because almost every single user is promoting site, interesting thing is that you can't promote it on facebook unless you use short links
use your browser to mine
Do research about monero CPU mining. Make your own conclusion.
If you can, make a small deposit on there (30000 satoshi) so that you can start earn interest everyday and you won't have captcha anymore when playing free roll.
Little above 4% annual is nice but in my honest opinion if you want to invest invest in gambling site bankroll.
Also there are no tricks to win multiplier game, if you are lucky you will win if not...