To air my suggestions, buy into any of the top coins on coinmarketcap, they will save you a lot from uncertainties while keeping you on a good position to know more about other coins. Starting with Bitcoin, you wouldn't have to worry if you are going for long term, but if for short term wait to know the right time to buy, others are ETH and so on. My reason for not saying new altcoins is that, a good number of them can't be trusted and even if you want to, let it be for a very short time. In addition, some of the things to look at is, the team, the idea or use case, the working products, the community, the partners, their social media activeness and exchanges.