Experienced traders will prefer to buy altcoins because the price is more volatile than Bitcoin which makes it easier to make a profit. Altcoins also experienced big pumps that could make one make more profit within a short period. But the risk involved in trading in altcoins is great because it can also experience a fast dump or drop in price which could culminate in losses.

When it comes to investment, Bitcoin is the surest and most reliable cryptocurrency. If you understand the Bitcoin market and are patient enough, you will never lose money investing in Bitcoin. $100 might be an insignificant sum to invest because you might not make so much profit even if the price triples but it is a good beginning. In Bitcoin, you invest what you have and why you can afford to live without it. So it the sum is what you have, I suggest you buy Bitcoin and keep it in a non-custodial wallet preferably Electrum. You might consider using a hardware wallet if you can increase your Bitcoin hodling over time.