you will need a bottle of pure argon and a new liner also use the next size up tip for ali, when usng ali wire back off the feed tension roller till it stops feeding then tighten the tension till it just starts feeding(otherwise you'll crush the wire), as for steel you have a choice you can use co2(but this cools the weld too much, but is better than flux wire), better still use co2/argon mix,also with steel preheat the weld area, just attack it with a blowtorch(till the metal goes a yellowish colour dont heat till red) , this should give you a much easier and nicer looking weld than with the flux core, oh and dont forget to swop the wires over so the torch is live(for gas )
hth
smeghead