What to buy?
If buying more than one dictionary, say on the Monokakido app (for example), what combination of dictionaries would you suggest? For best coverage of terms in general, or terms plus idioms and such, or some other reason.
I know you’ve put the Monokakido dictionaries in the order you’d recommend them in the post Making the Monolingual leap, but I wasn’t sure if you’d actually recommend buying the top three, or if some other combination might be better.
Answer:
**While my exact recommendations would vary a bit depending on the person’s level, the amount of dictionaries they are looking to buy and how they want to use it, my general advice would be :
If you are just buying one dictionary :
Read up on the entries for whichever one has your fancy (But 明鏡国語辞典 is a great starter one, and the one I would most thoroughly advice)
Two dictionaries :
The first one again should be the one that has your fancy, but the second one depends on which of the camps your first one falls in, if your first one was from camp A I would suggest picking one up from camp B for best coverage / biggest variation in explanations and vice versa (Note : I have arranged them in each camp in the order I would personally recommend them for a general reader at this point in time, though this order can change depending on personal needs) :
Camp A (simpler dictionaries) :
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明鏡国語辞典
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三省堂国語辞典
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三省堂 新明解国語辞典
Camp B (broader dictionaries) :
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大辞林４
-
日本国語大辞典
-
大辞泉
You want to buy more than two :
It’s only after you have already bought more than two dictionaries that I would start to consider Kanji dictionaries, but a thesaurus is a fantastic tool to explore your dictionaries deeper, and I would advice picking one up as soon as you are in the market for a third dictionary. My main recommendation would be 日本語シソーラス 類語検索辞典 as I fall back on that one a bit more, but both picks are quite solid.
For slang and the like 三省堂国語辞典 has a modernist approach to their dictionaries, so you are most likely to see current terms and the like reflected in there.
As for the best for idioms and the like, See Chapter 7.2
I’m not the one you asked, but I have an opinion anyways 
One thing worth considering is that of those six, you already have access to Daijiten (kotobank), Daijisen (goo) and a version of Daijirin (macos/ios native). So as long as you don’t mind going outside of the app in a pinch, you get more for your money buying the others. (At least I don’t think Meikyou, Shinmeikai and Sansedio have web versions?)
Having used all six of them for a while, personally Daijiten is my least favorite, especially considering how pricy it is.
Imo Shinmeikai is the one most worth getting, because of how different its definitions are from the other dictionaries. It being a bit wordy makes it hard for someone new to monolingual dictionaries, but after a while it became my favorite.
You’ll probably want at least one with lots of headwords for decent coverage, which I’d get either Daijirin or Daijisen for. I know Daijirin is fairly cheap when its on sale, but you already have a version of that on all apple devices. Not sure about the Daijisen price 
That leaves Meikyou and Sanseido. Both have fairly few entires, and both feel like simplified versions of other dictionaries at times. (Meikyou for Daijirin/Daijisen and Sanseido for Shinmeikai). Buut they also bring their own benefits. Sanseido has the most concise entries and is also cheap. Meikyou is probably the easiest to get into and is great for looking up grammar.
… a bit hard to narrow it down because I love all 5 in some way 
I’d probably look at price tags when the back to school sale happens in April and base the final decision on that :3
EDIT:
Realized this isn’t much of an answer, so if I had to uninstall all but three dictionaries I’d personally pick
Shinmeikai
Meikyou
Daijirin
… and perhaps Sanseido because it’s like 10$ on sale? ~~
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