Those on an even more limited budget will find interesting the free resources available not only from the Bible.org.uk website, but also via LuLu. I've provided an index of those resources, below, for my readers' convenience.
Greek NT (Critical Editions)
Apocryphal / Patristic Materials
I have linked only to the "free" items. There are other items available as well. There are also some more questionable items. For example, the web site contains a Russian translation of one of Ellen G. White's works, which is disappointing to see.