My holding are :
BTC = 70%
ALTCOINS = 30%

Sometimes i used BTC as to buy alts when there is some good alts on the market and has the potential to grow in value. I don't usually trade BTC but it still depends on the price, in BTC im a long time holder, in eth I'M doing a short trade and same goes for some alts nut some alts are really good to play with. There's nothing wrong to hold the main coins, the only disadvantages is that the main coins might go down and you might lose everything but if it goes up like ETH this year you will be a instant millionaire. It is always better to diversify it in a way that it will balance the price and you will not lose your profit at red time, it will be hard at first or the second when trading but you'll get by and learn from it. Remember the Famous line " Just buy what you can afford to lose ".