1) you should have suit pants anyway
2) as for shoes, just get NON SLIP black shoes you can buy them at Payless or any other cheap shoe store
You'll 99% likely get the job dude... They just want to see you work hard, smile, work fast, be friendly but not creepy, and do your job without complaining.
It's not rocket science.
If you have doubts that you can even do that stuff above correctly, then you're basically useless, lol.
I recommend you work at McDonald's instead of subway tho lol. The pay at those places suck. But at least with McDonald's it teaches you to be humble and work very very hard.
Subway you don't work as hard, so it's basically a useless job.
I make over $200,000 a year running my own business now, and my first job was McDonald's actually