Since we are going through different circumstances, I think minimizing the ratio OP have mentioned would be a better idea; try atleast 1/4 of your salary or monthly earned money. Take it easy and lightly because not all people here has privilege to do as they want with their earnings. Some are even accountable and responsible to give more than half of their monthly pay out, to their families which makes it hard to save. Especially nowadays wherein the market price of market goods are continuously increasing week after week.
The theory for investing with money sharing as above looks easy, but in life of course there are many challenges, I have been working for about 5 years and it is very difficult to leave money for saving, especially for those who are already married and have children, of course it will be difficult, and in my opinion the solution the best is an investment that can produce productively.
You're right but the question is can you invest with a one month salary? Definitely no! You have to save first before you invest in whatever you seems to be profitable for you. The important of savings is not only for investment but also for unexpected challenges. I actually don't know why people always attribute problems to married people and assume singles have less problems. Lol
Proper segregation and management of one's money would be the key. Try to atleast plan an amount for a certain bill; electicity, house rent, food, and such). If there will be remaining amount outside your dated bills, you are free to use it on investment or just save it in banks.