There is really no ideal coins to buy at this point in the market, anything before the ETF agreement will be under a big questions mark. However, BTC retains a lot of the market's volume and is dominating the market a lot more than other Alt coins right now. I would suggest in your case to perhaps split your invested amount into 50%(to HOLD btc) and 50%(to be used on either trades with alt coins or just buying and holding altcoins). If that is what your objective is, try to be smart and don't invest all your money into 1 coin or 1 buy always spread it out. Don't forget to use the stop-loss if you are trading as well to counter this market's volatility and crazy whales who love to cause these rollercoaster rides.