While it is not certain that your income will increase as you accumulate Bitcoin, it is a good idea to have some discretionary income in your reserve fund.
All people need to have reserve fund, small or big it depends on your financial availability and affordability for having a reserve fund but it's wrong to say a newbie does not need to have a reserve fund.
It is best to start without a reserve fund if you are determined to stick to your plan and are willing to invest in Bitcoin, as this will at least give you a chance to find a way to continue investing long-term while you are still in the market and have a good chance of getting involved.
Reserve fund means it will be used in emergency like accidents (transport, health, ...) or even when you suddenly lose your jobs. Without a reserve fund, your life will be very uncertain and can be broken anytime. The bottom line is you don't need too big reserve fund if your finance is not too good, but it's vital to have a reserve fund at least to live for some days, some weeks, and if better for heatlh emergency and so on.
If you are trying to increase your income or are looking for another source of alternative income, you can increase your Bitcoin investment even further. It is recommended to gradually increase the amount of your backup fund to protect your investment, perhaps at least three months of your family's daily expenses. And the focus should be more on starting Bitcoin than a reserve fund regardless of the reason and amount.
When your income improves and becomes better, you can increase both your reserve fund size and investment capital size. That's how I say your reserve fund is necessary but it can be small or big, depends on each person and personal financial status.