The rule of thumb is only invest what you can afford to lose. You’re new to bitcoin and even though bitcoin is a very good investment, it can be confusing for a newbie investor. It seems to me that $100 allowance you receive from your dad is inconsequential to you and it won’t be too much trouble if you risk it. You already have the zeal to invest, what you need to do now is to learn where to buy/sell bitcoins, how to choose bitcoin wallets and how to secure your wallet.