I watching some altcoins which the bubble are very big. I mean if bear market happen the price of those coin will fall very deep, but it's not a bad thing for contrarian investor like me. Honestly, this one of many reasons why I bought altcoin too. More than 50% of my fund is allocated for btc, and the rest are divided into several altcoin such as ETH, TRX, DASH and etc. Some altcoins has very big potential to get big market share, so in line with company's growth the price of that altcoin will be rise, when all infrastructures are ready for those companies then the price of those altcoin will rise like a rocket. For example is TRX, this coin price is already rise 100% from the lowest point at bearish market, I bought it at very cheap price, today the value is double. I still prefer like to invest in BTC rather than altcoin because altcoin still very depend on the company itself. Government regulations and other economy factors will affect those altcoin.
For quick and big profits, you may consider investing in altcoins but if you want to be 100% safe in your investments, then your best option is bitcoin only.