Xpath following the for the next thumbnail - optimized solution? (for selenium automated solution) - selenium

Question

At demo store we have a list of thumbnail as given below :
<ul class="product_list grid row">
<li class="ajax_block_product....">
<div class="product-container">
<!-- at this level ist the thumbnail number 1 -->
</div>
</li>
<li class="ajax_block_product....">
<div class="product-container">
<!-- at this level ist the thumbnail number 2 -->
</div>
</li>
<li class="ajax_block_product....">
<div class="product-container">
<!-- at this level ist the thumbnail number 3 -->
</div>
</li>
</ul>
I can navigate through thumbnails using the xpath mentioned below:
thumbnail number 1 = //div[#class="product-container"]
thumbnail number 2 = //div[#class="product-container"]/following::div[#class="product-container"][1]
thumbnail number 3 = //div[#class="product-container"]/following::div[#class="product-container"][1]/following::div[#class="product-container"][1]
Through, above xpath are working fine for me but not an optimized solution.
Update 1: The objective is leave the xpath in a closed "form" at web page object library, for using by automated tests.

Answer 1

Get all the thumbnails in a list and then navigate through. Use below CSS selector for the same. Not sure which language you are using. I write this using Java.
List<WebElement> products = driver.findElements(By.cssSelector("div.product-container"));
for(WebElement product : products){
String productName = product.findElement(By.cssSelector(".product-name")).getText();
String productPrice = product.findElement(By.cssSelector(".right-block .price")).getText();
...
}
OR using the xpath mentioned by you.
List<WebElement> allThumbnails = driver.findElements(By.xpath("//div[#class='product-container']"));
for(WebElement thumbnails:allThumbnails){
String productName = product.findElement(By.xpath(".//a[#class='product-name']")).getText();
String productPrice = product.findElement(By.xpath("//div[#class='right-block']//span[#class='price product-price']")).getText();
...
}
UPDATED
As per your comment if it is require to mentioned fix element in your xpath then using indexes would be the right approach.
there are total 7 product present on the page you shared the URL and xpath so you can write it like-
thumbnail number 1 = //ul[#class='product_list grid row']/li[1]
thumbnail number 2 = //ul[#class='product_list grid row']/li[2]
...
thumbnail number 7 = //ul[#class='product_list grid row']/li[7]

Answer 2

If all the products share the same class you can just have Selenium pick up all matching elements, as opposed to explicitly stating one after the other like you're currently trying.
You've not said what language you're using, but here's what it'd look like in C#:
// Setup your web driver...
var thumbnails = driver.FindElements(By.XPath("//div[#class=\"product-container\"]"));
foreach (var thumbnail in thumbnails)
{
// Do work
}
Or
for(int i = 0; i < thumbnails.Count; i++)
{
// Do work by index
}
Note the plural FindElements, it returns a collection of all matching elements. Selenium does a fairly good job of matching methods across languages so that should point you in the right direction at least.