If you do not know how to trade then I think this is the best amount to learn all the basics and learn to trade in the market , and of course choose the right exchange and study the indicators!
And it seems to me that starting with $ 100 is somehow meaningless. It is better to trade on a demo account and fill in some bumps. I think at the initial stage you will have many failures and thus losing your money will be very disappointing. Perhaps you will fear in the future and you will feel constrained on the exchange.
$100 is not a small amount of money nor a big amount of money but everything that is big now has started a while ago as small, and every cent in investment should be counted.
A penny is counted because if we split our investment into multiple currencies/tokens then it's the same like splitting $10, $1000 or $100000 because you divide in %.