Well, you want to look at the total memory bandwidth, keeping in mind that GDDR5 is faster than DDR3, often by a wide margin. (Meaning, 64-bit GDDR5 cards often have more memory bandwidth than 128-bit DDR3 cards. What makes that hard, is that some lower-end cards like the GT 730 that can still be used for low-end gaming, may come in a 2GB DDR3, or 1GB GDDR5 version. Which can make it hard to choose, because some games really require a 2GB card at minimum these days.) Better would be 128-bit 2GB GDDR5, but that config oftentimes means a different card model, such as a GTX650ti or something.
Low-end cards for gaming, are really a minefield that you don't want to be stepping in. Sure, they are "cheap", but for a reason. I mostly bought several of those Zotac 1GB GDDR5 GT730 cards mentioned recently in the Hot Deals cheap video cards thread, because for $40 they can do 4K60 output. Gaming was of a secondary concern, but according to a YT video I found, they can play GTA V, at some lowered settings, with a quad-core CPU. Which is a nice bonus feature.