Of course $100 investment is worth it. If you take $100 and do 1 trade everyday and make a 1% profit then re-invest everything you've made and do that everyday for 2 years, you'll have over $1,000,000. Compounding interest really adds up quickly!
That's the theory. And it never goes 100% as you want.
$100 is not much, better to buy very low priced altcoins that can double fast your investment...or half your investment.