Here's a list of "essential" items to use. I don't want to re-invent the wheel, but a lot of these are on Simtropolis, so instead of going through what I would do, I'd just like to append their list a bit and give further clarification and recommendations.
First, download the patches (if you don't have a pre-patched version like what's on Steam or GOG) mentioned here that are hosted on SC4D. Follow those links down to the "BAT Nightlighting" update. If you can't access those files, please contact me and we'll work something out.
The Network Add-On Mod is another one to have. Again, because of both updates and the fact that it's kind of immoral at best to re-host it here, check out NAM here. The NAM has its own set of settings. I like RRW but don't like the redrawn textures (it makes curves integrate more but adds cul-de-sacs to everything). Play around with the settings.
The "Top Ten Modds thread also recommends this high-speed rail mod. If you don't intend to do anything with it (I didn't), don't bother downloading it. I never tried it.
Basically everything on the list is good, though I never got the hang of #8, the Day-Night Mod. The "nights" in SimCity 4 never go more than a twilight blue. The mods can get night to an even blacker state, but it's not fully compatible with many of the existing "nightlights" of buildings and can slow older computers down. The former is a problem because when testing it, some lights that used to appear normal appeared as this hazy purple (such as the High Mast Lighting listed below), and otherwise everything was too dark, less "night on the city" and more "9th plague of Egypt".
The other one I do have a bit of a problem with is #2, which adds cars and other clutter to street sides. It would be great if you were building a really urban NYC-esque city, but like the HSRP mod, I never really built cities that way.
The extra cheats mod is highly recommended. It's a DLL, which is only accessible to Windows users (sorry), unless your Mac version is directly based off of the Windows users (and uses some sort of wrapper).
Finally, most all of the fixes mentioned here. Search for "no radiation" too while on that note.
In other news of what I like but isn't already mentioned, let's start with the high mast highway light towers. I was delighted to find these a while back because they reminded me of highway light towers found in other locales (such as south of town, though they aren't there now if they were ever, or more specifically Houston), which were great because that meant you were going on a road trip. Later on, some were built as part of an overpass project so I see them literally all the time now (just looking out my bedroom window), but the memories remain.
Speaking of all things high-mast, remove those candy-cane striped power lines with this mod.
This is admittedly kind of a "cheat" item, but I love the Geothermal Plant.
I'm not sure if this works on the Mac version (which I haven't used in years) but this is very recent—SC4Fix. This December 2015 mod fixes a bug involving hovering transit-enabled items over each other, causing the system to crash. Most users of NAM have encountered this before.
More to the list to come...
September 14 2015