I also suggest to invest in Bitcoin first as if the market will go to high then first of all the price of Bitcoin will go high after that the price of other coins will follow. I often do that I invest in Bitcoin and when the remaining coins start to increase then I put my money to there.
At the time when the Bitcoin price increase starts, the prices of all other altcoins will grow much faster, as can be seen from the change in the price of altcoins when Bitcoin grows. It may be worth choosing a few promising altcoins for investing in order to get the maximum profit, for example TRON, Stellar, EOS.