I've seen a lot of Youtubers promote cloud mining and the first thing they do is run to Coinwarz and Cryptocompare, punch in the numbers and look at their annual gains.
These numbers are inaccurate.
For eg. on 50TH, it might tell you that you will earn 2.8btc a year, where in fact, it might (big "might" as difficulty is hard to predict) only be 1.2btc.
This is because of difficulty increase.
What I would personally do on Hashflare on a 50TH contract, is to compound until you get a daily gain of 0.01. Maybe start profiting then and as soon as, due to difficulty, your daily goes below 0.01, reinvest/compound your way up again.
Try and sustain that 0.01.
With my horrible math and spread sheeting, I managed to see an increase in annual gains and your contract stays active. I'm not sure what the math would be if you increase and sustain your daily payout to something like 0.02 or 0.04, could be better.
Note: please don't take what I say as fact, maybe Cliff or someone smarter than myself can do the maths more accurately.