In that case, I think I'd suggest getting both
Madame Crowl's Ghost and
Through a Glass Darkly. While each has both some of his best and some of his more obscure (and sometimes weaker) stories, together they represent the majority of the contents in the Dover volume; and whereas
Madame Crowl's Ghost does not contain either "Carmilla" or "Green Tea" -- certainly the most famous and perhaps most important contributions he made to the short supernatural tale --
Through a Glass Darkly does... allowing you to have much of his best for considerably less. It's a pity, though, that you won't also have "Ghost Stories of the Tiled House"; but, if you like LeFanu enough to want to look that one up (and it, also, is one of his most disturbing pieces), you can find it as either one of the early chapters of
The House by the Churchyard or in Montague Summers'
The Supernatural Omnibus... which is itself chock-full of really superb selections from the weird tales of the Victorian and Edwardian eras. (Summers may have been a complete loon, but he often showed considerable abilities when it came to gathering either information on the Gothic tale or collecting together very notable examples of the supernatural in fiction.)
The following link, while not providing the full text of Summers' volume, does give you the full table of contents, and texts of quite a few of the entries:
Introduction to the Supernatural Omnibus (1931) by Montague Summers
"Ghost Stories of the Tiled House" is here published as "Narrative of the Ghost of a Hand".
I would suggest going with Summers' rather bulky anthology rather than LeFanu's novel, despite my own strong fondness for the latter, because I rather doubt you'll find it to your taste. Not many people today do, I'm afraid (though M. R. James certainly thought highly of it, as I recall). It is a strange, meandering thing which, nowadays, takes a certain type of reader to enjoy it. Certainly Teresa, who herself has quite a fondness for books of the period, found it tedious (and, as I recall, annoying) going. On the other hand, Summers' book will provide you with an enormous amount of truly excellent material (as well as some lesser, though still entertaining, examples of the form), and it has had numerous editions (and usually several printings in each, as I recall), so should be acquired fairly cheaply.
Speaking of which -- going on something you said elsewhere: no, you don't sound like a skinflint, or miserly, or anything of the sort. You sound sensible and frugal. After all, unless there is an overriding reason for putting this sort of thing as among your top priorities, there's no sense in going too far at one time, when you can get a better bargain, or perhaps find the desired book at a later time for less. And, with things like this, now that they have been brought back into print in mass-market paperback editions, it should be fairly easy for you to find copies now and again for very reasonable prices. It isn't as if these are modern best-sellers that will flash and fade... these books have had a reputation for well over a century now, and have enough of a following to keep them from fading away for a very long time now....