Hey,
So Ive invested into couple of coins and currently holding them on a exchange. Is it good idea or should I download a wallet. For an example what is good wallet for Ripple
Regards
Don't store most of your altcoins on exchange if you'll only going to hold them for a long time. Download their respective wallets and put it there so if anything happens to the exchange your coins are good and safe. What are these altcoins that you did invested to? Everyone will say here that don't store your coins on an exchange if you have sums of those, you can put a little amount if you'll use it for day trading.
But if are comfortable without it that's your wish.
It's still the best thing to keep it locally stored with private keys.