The only apps that can do trades right now are the mobile apps for the various exchanges. And to view the market and coins available, the most popular site/app is Coin Market Cap. But there really isn't one that can handle everything for you. Which is why I'm currently building out an app called Matrix Portfolio, that will help you automatically pull in your trades from exchanges, so you don't have to manually enter them. As well as allow you to discover all the coins, and offer trading insights as well. Feel free to pre-register for the beta here: http://matrixportfolio.com
A successful strategy regarding this is placing very low buy orders. About a week ago a crazy dump occurred, selling off Augor coin down to 25% of its value! After a short while the market recovered slightly and anyone who had low buy these low orders could easily double or triple their investment. Placing buy orders requires special care, don’t wake up when you’re far away from the market to find your buy order is suddenly higher than the current market price!
Always pay attention to Bitcoin. Most altcoins (every cryptocurrency except Bitcoin) are pegged more closely to Bitcoin than Asian currencies were to the USD during the Asian Financial Crisis. If Bitcoin price pump drastically, altcoins price can go down as people try to exit altcoins to ride the BTC profits; inversely, if Bitcoin prices dump drastically, altcoin prices can go down, too, as people exit altcoins to exchange back into fiat. The best times for altcoin growth appear when Bitcoin shows organic growth or decline, or remains stagnant in price.