DOGE, LTC, Ripple, Ethereum - basically read a lot about what is going on with altcoins, just like you would any corporate stock.
Of all these coins, I would only invest in ETH. In the success of other coins, I do not believe and do not advise most of the money to invest in these coins.
Honestly not all Altcoins are worth it to buy because some of them are no longer around or scam coin, that's why you need to be careful of buying crypto. Also before you buy make sure you know or you have research about that coin, or else buy those coin that have potential so surely can bring you profits. I recommend you to buy Ethereum because it is one of the successful and 2nd to the highest value to all crypto, then this altcoin is possible to grow even more.