From the beginning you should understand that Altcoin investments suggest huge risks. However, if you have decided, then learn the projects from the top-20 or the top-30 of the Coinmarketcap. And take the projects whose team actually follows the roadmap. Perhaps, there will be among them such projects that havent pumped yet. Only these projects can generate higher profits.
Not only Altcoin but also Bitcoin investments suggest risks because 'Investment' is more likely playing a game, you give your coin, your time and your full effort but there is no assurance of winning it. So before starting to invest, better to have the knowledge about it. And most importantly, you should know how to deal with it using the knowledge that you have learn so that there will be a greater chance of bringing home the bacon.