There are two important points with what to wear. First, wear form-fitting clothes. These are clothes that are tight to your body and not baggy anywhere. This is so the viewer can easily see your physique, which is a main goal when submitting your digitals to agencies. Second, is wear dark clothes but they should also contrast well with your skin tone. If you are very dark skinned or very pale, opt for medium gray or similar so your outfit doesn’t blend too much or contrast too much with your skin tone, respectively. If you are a more common medium skin tone, then opt for darker colors, such as black. For shoes, most women wear heels and men wear dark sneakers. Another important thing to note is minimize accessories and also any business on your clothes – minimize or eliminate logos, stripes or patterns, etc. Solid colors are best.
For your second outfit, pretty much anything goes as you should consider targeting a niche so you can start to build a portfolio – fitness, swimwear, high-fashion, etc.