People already fortunately have the recommendation towards IDW TMNT covered, along with the fact that the micro/side/etc series DO matter and are great (it really is kind of like the book has been effectively double shipping, to be honest, which is fine by me since the quality is absolutely there to support it). But yeah, TMNT/Ghostbusters, while fun, is totally skippable.
Did want to add, though, since the stuff is also on sale: It's NOT for everyone, but if you're interested in the older stuff, what you want is the first 5 Ultimate Collections (the 6th was bits and pieces they scraped together later, so you don't really need it), and the first two volumes of Tales of the TMNT (which was essentially a side series to the original and contains some good stuff. The volumes afterwards are actually something completely different, to add to the confusion). Like I said, not going to be everyone's cup of tea, but it's some solid old-school indie goodness, and that's definitely the stuff actually worth considering, as outside of those you get a good bit of dicey stuff.
But yeah, if you haven't read it, IDW Turtles is definitely the one to get and is amazing. I get the confusion since it's not ideal, but it's worth going through the whole thing, miniseries and all, as it's great stuff. Oh, and just in case the books make you think otherwise as I think they DO get a tiny "see *" note somewhere, the annuals are totally skippable for IDW Turtles. They're essentially old-style Turtles stories (in terms of both art and writing) that are technically part of the IDW continuity, but not in any significant manner whatsoever.