A strategy (with some risk ) would be to buy Ethereum ( or any altcoin , but Etheruem is safer ) and when the ETH/BTC ratio improves , you trade for Bitcoin.

This way you get more BTC for your dollar.

The risks - ETH never goes up in value , or maybe it does but BTC outpaces it , meaning the ETH/BTC ratio doesn't improve significantly.

Lets say you buy ETH at $600 , and if the ETH/BTC ratio goes to 0.1 , you trade for Bitcoin , then the effective BTC price that you paid is about $6000

Watch this video for full information , but just a thought : https://youtu.be/Phutr1ulrYs