Can someone make it trading only altcoins?
yes actually its possible but you need to learn how to read technical analysis before doing a trade I know a persons doing that and earn around 10-50% in daily trades h. But that's not always accurate that's why its important to have stop lost if you don't want to lose large amount in trading.
If you really interested learning it watch many tutorials or attend seminar to have ideas and learn how to do it.
Technical analysis, research, predication and quick decisions are important if someone is going for quite trades. People lend money on 10-15% interest for a month or even year, but in crypto currencies you could make that 15% in a day or even within minutes for a matter of fact. You should know the market inside out for that and keep an eye on the coins. And yes, stop loss is always there to save you from drowning all your investment. so be sure to make the right use of that feature before you go all in.