Yeah your right its unpredictable but its depends of your strategy and what altcoin you choose..
In my opinion or tips i think better to always use coinmarketcap and choose top 20 altcoin or top 10 altcoin and choose them because those are legit altcoin that you can hold for a long time.
I can really say that trading can be unpredictable because no one could ever be so sure of it's outcome in any kind of trading transaction one will make. It's risky but less than gambling. You just need to deal will small amount if it's your first time in trading because it's hard to lose big amount of money in just your first time. Just atleast you will be familiar in it's processes and you'll have an idea in every transaction of it. And don't ever forget to just invest in trading what you can afford to lose so you'll never regret.