[edited out]
You are right, investing without having a discreet income after spending is risky, investing money that we can lose. If our income is low, we should reduce unnecessary expenses and pay close attention to our skills, as well as take some training that may not yield results now but will be in demand in the future. We should plan not for the present but for the future. It is normal that expenses will continue to increase over time, but as the amount of expenses increases, it would be wise to apply your skills through training to earn additional income. If our income is low now, it is possible to increase it in the future through your skills. Even if this plan does not yield immediate results, it will greatly help in properly planning future investments.
Generally speaking income does not keep up with debasement of the currency (as prices go up), except people who are younger are likely to be able to get greater and greater income by receiving promotions, and like you suggested there are some folks who have high skills and are able negotiate higher wages and/or promotions.
In other words, there are a lot of normal folks who either have fixed incomes (such as persons drawing retirement income and/or pensions that do not tend to adequately adjust for inflation) and persons who have low paying wages and their wage increases are way less than the increases in the cost of living.
It is wrong to presume that everyone is in a position to negotiate higher wages/income, even if it is possible for some. There are likely folks in dead end jobs and low paying positions that could put themselves into a position of building their skills and/or experiences so that they can get higher paid jobs and/or promotions.
The relationship between income and currency debasement is indeed very complex and if we really look at it, we'll discover that not everyone's income keeps pace with inflation. Individuals who are on a fixed income, such as individuals who are retirees, often rely on pensions, and they're often faced with the challenges of maintaining their purchasing power as prices rise due to inflation.
Even low wage workers also are faced with the challenges of stagnant income growth, with wage increases, with the inability to keep up with the cost of living. The ability of individuals to negotiate higher wages or securing a promotion is most likely dependent on the individual's circumstances, their skills and also job market conditions.
And even though there's actually a possibility for some folks to potentially take proactive steps towards building and improving their skills and experiences in other to increase their earning opportunity, this approach isn't universally feasible. There are often so many challenges that may likely hinder a lot of individuals from making this move, such as limited access to proper education or training, lack of potential opportunities, family responsibilities and obligations, these things are enough to hinder some individuals from actually moving forward or making some moves to potentially enhance their earning opportunities.
Although, the notion that folks can simply bootstrap themselves out of low paying jobs kinda overlooks the structural issues that potentially contributes to income inequality, because there are certain sectors that are actually characterised by low wages, limited mobility and even limited opportunities for advancement.