Your pre-vocational course at Tafe is going to be your best bet.
If the selection comes down to 2 applicants, & 1 has the pre-voc, guess who's going to get the job?
Some welding certificates can be done without a trade as a prerequisite. Usually they are done at night. They are reasonably priced too.
Anything you can do to show initiative is going to be in your favour.
As mentioned, a forklift ticket might also be an advantage, but not if there aren't any forklifts in your future place of employment.
Take out any facial piercings prior to the interview. Employers don't generally care about your appearance, but any employer in the metal trades will frown apon having to pay workers comp because your piercings got too hot & burnt you!
Show up to the interview in battle dress. [ safety glasses, work boots, long pants & long shirt. Wont hurt to have a welding shield & a pr of gloves under your arm]. You probably wont need them, but it shows you are keen. If you are in battle dress, you stand a better chance of being shown around the complex; which; gives more opportunity to 'meet' your prospective work m8s & make that all important 'first impression'.
I've been in the metal trade for 30yrs. I don't care if someone wearing a T-shirt & thongs disagrees.
Oh...... finally.... don't whinge about your wages for the first 2 years. The low pay rates are there to discourage apprentices. It weeds out the 'I'm going to be's'...... from the 'I'm just here for a job' apprentices.