Most Helpful Guy
Hat will help way more than the hairnet, for sure, so keep that trend up. It's pretty much impossible for a girl to look good in a harinet. Good jeans can go a long way. Shame about the shoes, that can go a long way too - unfortunately I can't actually imagine anything uglier than Crocs, so I think that must be pretty bad.
Little things can be done with the t-shirt, depending on the dress code for the kitchen (the kitchens I worked in varied tremendously on what they would allow). Rolling up the sleeves a little bit helps make them look more feminine if it's a guy's style shirt (girls t-shirts have shorter sleeves, in general).
Make-up, sure, that's obvious, but something you don't want to overdo, because it will really clash with the rest of your look being so casual. Little bits of jewelery can add a bit of color and flair as well. Guys in the kitchen are not going to be expecting you to look like you are about to go dancing, so it will be the little things that add a bit of femininity that will have a positive effect. A touch of pink in a bracelet or a necklace, though a bit cliched, will help reinforce "look, this is girl" in the back of the guys heads.
Just be subtle, but find little ways to reinforce that you are a girl.
Most Helpful Girl
I would suggest finding a time of jeans that really flatters your body and that stand out, some sort of detailing on the pockets always looks nice with dark or black jeans and there are lots of acid wash or mottled blue jeans that are cute with just about anything. For the t-shirt I would go with a bright colour or something that stands out. Dark blue jeans can be hard to match with certain colours but, black goes with just about anything along with light coloured jeans! That's really all that I can think of but, I hoped it helped at least a little bit!