maybe he doesnt read the op's question i guess. buying bitcoin in $100 amount would be small to keep it for a long time, with that amount i would rather invest it into trading and do my best to make it grow with it just avoid on lossing trade it cant be possible but be sure to do smart trades so that your $100 in bitcoin would grow not just on holding it.
$100 is not really a small amount for everyone but it is small if someone is wishing to hold his coins so for that he would need to grow them a bit by trading altcoins which can generate him good profits gradually even if he starts with $100.
Well for people who are saying that $100 is a small amount well get yourself lives guys for us who are not that wealthy that is already a big amount for investing into something so that we are going to make it grow. And there are only 2 ways that I can think of for investing it by trading and by just keep holding for it.
I think $ 100 is enough large for trading, I just capital only 0.01 BTC or around $ 10 can already generate a hefty earnings, depending on the intentions and stretegi you in manage
also it's depending about your skill, not all people have "good brain, tactic, plan, or highest IQ" to learning bitcoin/altcoin trading, i think start with $10 is better to get more experience, then we start trade with highest capital without any skill.