If you want to look for coins that can 2x - 3x in the future, you have to determine the time you will hold it. Many coins need long time to able to reach 2x - 3x but some coin just need 2  - 3 months to make this.
I recommend 2 coins which can 2x - 3x in 2018.
HOQU: is the first decentralized marketing platform that allows merchants and affiliates to interact directly without brokers and ensures fair cost per actions deals based on a smart contracts. HOQU have good project and good team so potential will 2x in 2018.
AMLT: The Coinfirm AML/CTF Platform and its AMLT Network aims to build the global standard for AML/CTF enabling transparency for cryptocurrency and blockchain based transactions. AMLT is having an successful ICO and the price of AMLT coin will 5x in 2018.