That has always been my method for investing in Bitcoin. I don't have like huge amount of money to invest in Bitcoin all at once, so all I do is to take out a little percentage of my monthly income to invest. That way, I'm able to gather a lot of coins as time goes on. It's the best as it doesn't dry your pocket.
Even you have big capital, Dollar Cost Averaging is a good investment strategy for long term investors.
In other words, DCA is a good strategy for both big and small investors and with your small income, small investment capital you can spend for bitcoin each month, DCA will serve you very well and will help your portfolio increases in total value.
After you DCA many times, have enough big capital and feel acceptable with withdrawal on centralize exchange, withdraw your bitcoin to your non custodial wallet.
Reminder: do not keep your money in online accounts.