I would hold onto them for now. After you get a feel for what is accepted and what is not, phase them in after careful review of each image.
I would agree. Don't assume anything. In the beginning submit images that you feel really good about. You can put one or two images from the rejected batch in batches over the next few weeks or months. Look at other peoples portfolios and pay attention the the upload dates where available. Only teach yourself from the newer images you find. I say this because there are a couple hundred thousand images in IS form the early days that would NEVER be accepted today.
Always look at your images at 100% or even 200% for noise and artifacts. SS doesn't like noise. They aren't as hard as IS when it comes to isolation but you still need to pay close attention to the details. If you do that you will get your uploaded images accepted. Don't worry too much about rejections and never take it personal. I made that mistake in the beginning and almost quit. Don't get mad at rejections, just repair the image if you can and re-submit it. If you can't fix it in PS, you may want to re-shoot it before uploading it again.
I hope this helps and good luck to you!