Do you think it makes sense to invest in the cloud mining of bitcoin now?
No, it doesn't (has been like that for a long time) plus investing in cloud mining, is equal to giving money to scammers (in most cases).
There are a lot of cloud services with reputation, so I use them and they are paying. Moreover, there are some resources that monitoring scammers and other bad guys. I am checking them everyday.
But I'm asking about amount of investment to cloud mining to be in plus every time. Is there any formula or function, which allow me to find out which amount of investment can bring me most advantage?
No, because mining difficult is constantly increasing, the calculation you use today can't predict all the fluctuations in your income along the days, weeks, months. The only thing calculations can predict is that you won't recover the same amount of BTCs you invested. If you make profit it will be because Bitcoin price increased in Dollars while your money was invested on the cloud mining (talking about real cloud minings that are really mining).