$100 is an ok start if you want to put your money in a few cryptocurrency. Again, you first NEED to look at short term trades because you want to build up your portfolio where you can do asset allocation when you have enough of profits.
For short term trading I recommend the following coins/tokens: Ripple, Stellar, iota, Verge, Bytecoin, Bitcoin Cash, Tron, Zilliqa.
Wait for the market to rebound a little and fall then pick up 1 of them. Since you only have $100 now. Pick really any for a short term trade. Bitcoin Cash though is having a fork coming next month where it'll split itself into a new coin and the value of Bitcoin Cash will rise higher than now.
But again you're looking for a few short term trades to turn that $100 into $200 to $500 to $1000 and onwards. When you build up enough of your portfolio, say $5000 then do your research and invest in a coin/token you think will rise in value based on what product/service they're brining into this world and do you think it'll work for them?
For instance I'm an early investor in a cryptocurrency called Telcoin. One of their main missions is to "bank the unbanked". Meaning mainly in Countries for people who either don't have a bank account, aren't qualified for one or if they don't trust their banks, they can still receive payments from anyone in the world (probably mostly relatives) via their smartphones, like a text message without having to go through a bank first. This will not only include sending money or remittance but also payments, credit, various financial services and they even want to get into gaming later on. Incredible opportunity for a long term hold, I'm holding it. You can do your own research.
(I expect this comment to get downvoted a lot because it's cryptocurrency and crypto's are risky assets but now more and more they're becoming accepting world wide. A lot of people are still against it but 5-10 years from now they'll be on the boat with us and will be sad that they lived in a time that they could have become early adopters and missed their chances, you don't have to.)