I use these risers I got off of amazon. They're decent sized for my shelves I keep my nendos on, and they fit about four or five nendoroids on each level if they're on the standard base.

Got em on amazon, these ones specifically: BYCY 2 Pack 2-Tier Clear Acrylic... https://www.amazon.com/dp/B08KZQSLVR?ref=ppx_pop_mob_ap_share

I think most people put them on glass risers on either bookshelves or glass display cases. Baseball bat display cases are also a great way to display them and can be hung on the wall or just stacked up on a desk or something. They're also one of the cheapest dust-proof methods if you can catch them on sale, which they almost always are. They go on sale for around $30 on a regular basis. If you have a larger collection, the price can scale a lot though.

Here's some pictures with bookshelves: 1 2 3
Pictures with glass display cases: 1 2 3 4
Pictures with baseball bat displays: 1 2 3

There's more ways than just these of course, but these are some of my favorites that other people haven't covered yet

These are the ones I got, and here is an Imgur link to some of my nendoroids on one. It doesn't show off in my pictures super clearly, but you can easily fit four on each row if you have the stands all touching.