If you want to invest in a long term profitable asset and you don't have a discretionary fund you can do the following. Cutdown on your basic expenses if you can, get a better paying job, get a side hustle, learn profitable skills, do what you can to earn more than your basic expenses.
I agree with you though, for us to have a good discretion fund, we need to increase our source of income by learning skill and doing side hustle but cutting down expenses is what I find difficult. Already economic inflation is panting down on people and everything is becoming expensive so no matter how you cut expenses down it may never give a reasonable amount of discretion. Not that cutting down expenses is not good but it can only work in some cases and not all cases. The point is that there are some expenses that can be cut and there are some that can't be cut no matter the situation. So it can only expenses can only be cut if the situation permit. But however in most cases you need to work hard to increase your source of income to increase your discretion.