I wan't to join a gym so when I get to my goal weight I'm not skinny fat...

Melbourne, well down on the Mornington peninsula.

Also how should I dress for the gym?

I have an easier time to stick too a diet when i work out. It become more of a routine like that. I def think he should gym first and then diet.

runners, shorts or slacks, t-shirt
ie: workout clothes

An old t shirt, trackies or shorts, runners or other flat soled shoes if lifting.