The item will purchase by the end the day has not posted anything yet
If something isn't selling or buying immediately, don't become concerned. If it's not buying the first time, it's because you're purchasing below the average price, and only those who don't want to or are looking for cash can sell for medium prices. Generally, the item will purchase by the end the day.
If it's not sold or sell, it's either an item that's not in high demand or you've chosen an inferior item and the amount you've set isn't enough. I wouldn't recommend taking the price down until a week or two after you have put your offer out. Remember, merchandising doesn't happen in a single day; it requires some time and patience.
I'd advise buying everything you need on the g.e. If you're working with raw materials such as raw fish, logs herb, etc. I would suggest selling it in the streets for the same price per item.
If you're selling other items basically not-skilling items then I'd sell it on the g.e. It may take a while however, this is the best option and it's easier to locate someone looking for ten dragon platelegs than two thousand nature runes.
When you're first starting your merchandising, I'd suggest at a minimum of 10m or more. One general tip: don't be worried about losing money in the beginning. It happens to us all. When I started my first runescape game, I lost about 6m the very first day.
If you want to know more about RSorder, you can go to https://www.rsorder.com/