Whatever coin you choose, you should start with small amount of money to invest, so in case you loose everything, it won't affect you life much. Be smart, always make a research. And whether it is a top coin or not it should have a potential. No one can tell you will you get the profit or not, it's your choice and your responsibility.
Yes, you are right. Never let excitement take over your investor extinct. You may see a coin is going up like 10-15% daily so you plan to put all your investment in the coin but this is wrong strategy. Always try with small amounts at first and once you think you are veteran enough in market, then only go with full investment.