It's not compulsory for all new bitcoin investors to start with little amount of money as low as $10 in the beginning of their investments. Investors that should get started immediately with little amount of money are those who don't have large discretionary income or they have but are in doubt of bitcoin as a good place to throw some value in.
If you can start your bitcoin journey with $100, then get started. Those investors with large discretionary income can start their bitcoin investment with lump sum and then continue with their regular DCA every week to keep their bitcoin investment ongoing, persistently and consistently. Also they have enough flexibility to invest aggressively. Let's not misunderstand the concept on how to invest and our aim of investing.
The aim of investing is to accumulate as many bitcoin as we can with our discretionary income for 4-10 years and above, and also to try and invest aggressively if we can so that we can reach our bitcoin target fast. It's better to invest aggressively if you can in the beginning with DCA in a fast pace than invest in a whimpy way when you can buy aggressively.
Better safe than sorry, or in this case, better to invest a little than to not invest at all, bitcoin investment doesn't wait for anyone, so anyone who can start their investment journey with as little amount of money as possible should start, you don't need to put in a large sum of money before it can be called an investment, start small then grow the investment as you go, with consistency and dedication someone who started investing with $10 can ultimately invest $100 eventually as long as they keep to investing and not give up along the way.