I think that any amount of money is not less to invest. Because many people can afford to invest $100 and many can afford to invest $10. It is better to have some amount than nothing. There are many people whose monthly or weekly salary is very less. At the end of the month or week, they have very little money to invest, so continue investing with it. If you invest $2, it is not less.
When you are ready for DCA, you must think of several things that can affect your investment and bitcoin accumulation as well as results of your DCA.
How often do you do DCA?
How much you are afford to spend for each time of DCA?
The second question relates to whether you withdraw your bitcoin from a centralized exchange immediately after a purchase or have to leave your coins there for a while and must wait for several next DCA times before a withdrawal. It relates to your fund safety as well and it's important.
How many percent a withdrawal fee is in your total capital value?
If it is a big percent, you will have to delay your withdrawal for saving withdrawal fee but it increases risk of losing your coin by a centralized exchange issue that you can not control.