Use btcjam if you are a long term investor. Otherwise ponzi schemes like hyip will be nice if you afford to loose bcoz buying bitcoins itself a gamble
I think you did not read the topic or what OP is saying that is why you are suggesting btcjam to him, because btcjam is a loaning service which would require you to invest quite a large capital in that so that you can get some good interests on that, but 100$ is not that much, it is good for trading which can earn you some good profits in a short time with that amount.
This is right. trading is more profitable with less amount of money. and BTCjam is also good but need more time to get ROI(I didn't used BTCjam, I just heard from others)
but deference between BTcjam and Trading is
In trading you need to work hard your self and need to be active on trading. other wise you may loose,
and in Btcjam it is quite effort less, you just need to add your money in a loan and then wait for return.
now it is up to you.
choose the hard and difficult thing and earn money fast. or choose the easier one and earn money slower.