Maybe your best option is to upgrade. Starting with SQL 2016 SP1, Database Audit is supported in Standard Edition.
If you need to stay on SQL 2014, Extended Events or Trace are your only options.
In any case, if you insist on staying on SQL 2014, you should at least Service Pack3 and slap on Cumulative Update 4 for SP3, to get all updates for SQL 2014.