Personally I think skins are personal preference. Even if I leave a recommendation for you, it doesn't mean you will like it. Anyway, here are a few I think are good:
1. ExGon/Motion skin (large white squares)
Some people don't like squares (again, skins are subjective) but imo they work well for all mods you mentioned above. They're large enough to be comfortable to add HR, nice enough to read with DT and HD, and are pretty big which makes it useful in FL. I personally don't like their catchers though and prefer Yuzu (default).
2. rostld skin (decently large completely opaque white circles)
There are actually a ton of skins with white circles of varying sizes and different drops and catchers, but I like rostld's the most. This one is mostly great for nomod and HR imo but can be used for other mods too. Catcher's great. Also pretty nice to read DT on.
3. Dusk skin (decently large white outlines of circles)
I like this skin a lot when playing maps with edge jumps (mostly converts) so I guess this isn't for a mod but type of map? I usually use Yuzu for catcher, but otherwise great.
4. B-a-d-s123 skin (grey-ish small round fruits)
I don't use this a lot as I am not a hidden player, but it is pretty comfortable to read HD with this imo. Do give it a try if you plan on getting into HD.
5. [224]Reol skin (hard to describe)
Same as above, nice to read with HD.
6. [224]Hyperw7 skin (small yellow squares with a hollow middle)
I don't personally like this skin, but apparently some folks do. Apparently nice to read HR on. The catcher's also nice I guess but can never beat Yuzu :d
I'd say that's all I can remember off the top of my head. Some of these players may no longer use the skins I described above (if so, please correct me) and honestly I can't be bothered to link the skins (99% sure all of them have links to their skins in their userpage).
As you can see, all of the players mentioned above are top players with some even being among the best players of a certain mod, yet even they have different skins for the same mod. In the end, it's a matter of what you find most comfortable. None of these skins may even be as good for you as they are to me. Maybe default's even better than some (nah that thing's the worst). Just take my recommendations with a grain of salt :^)
For FL I also suggest looking into hit lighting especially if you plan on going into HDFL as well as using shift + tab (it helps).
Also, to finish off, try different catchers. I heavily recommended Yuzu because I liked it the most, but maybe you'll find a different catcher is more to your liking. It changes your reading quite a bit imo.