Before you invest, you must know that BTC is full of risks, you have to be patient and keep it, I believe the value of BTC will jump and make your investment grow. you can buy it in several exchanges by depositing fiat currency and exchanging it with btc
People do need to understand that btc is highly volatile and involved huge risk. Yes higher the risk even the rewards can be greater. So one should have patience and ready to take risks then only do invest in crypto currency else if you invest and require money then you might get struck if market crashes during that time.
You can't lose your money until you sold them. If you're agree to showing some patience then fell free to chose any plat form. My advice is chose bitcoin but only if you can handle your panic selling.