1.There isn’t a definitive yes/no answer to this I’m afraid. I would promote your other items where it makes sense; is the item you want to promote related to the one the customer is currently viewing? Would it be an item for them to naturally consider in addition to the current one?
Providing a link to another item does increase its discoverability, but one should ensure correct anchor text etc when doing so (see Q2)
2.I’m not an expert in UX and so have no input on whether you should use a banner or text; they both work in the same way from an SEO perspective, provided they are used correctly.
With text links, the anchor is taken care of for you; whatever you use as “the link” will be the anchor text, ie, the thing that Google etc consider as your target term. This should be relatively detailed. For example, using
background music as your anchor text would mean you wanted the target page to be a provider of that, but that term is so broad and competitive you likely won’t see any organic results. Using something like
saxophone office party music would be more descriptive and target your niche more accurately.
If you’re planning on using an image, then ensure you are using
alt tags correctly.
3.There is no
optimal amount, but keep in mind that any images or links are not considered part of your content; flooding a description with links to other items will see your organic performance drop as a result of spamming the user with links and keyword stuffing. Also keep in mind how many times you would be expecting the user to click on a link, then
back to get to the first item, rinse and repeat.