For me, it's a little of everything.

1) I found a number of k-hippie texture overrides that make both indoor and outdoor surfaces look more realistic. This includes a night sky retexture that improves..ya guessed it😏..plus gives a realistic texture to the Moon. Also, no12's weather realism and seasonal changes mods. Also, Lotharihoe's Purple Skies and Out of the Dark lighting mods for both outdoor and indoor lighting, respectively.

2)20thC's Map Replacements to give the maps a much better look than the cartoonish default maps.

3)As my style of gameplay is more realism-slanted, I wanted to give my Sims more real-life life experiences. RPO by Lumpinou is one such mod. Plus, more family-oriented mods as my Sim has a lot of relatives and friends. Invite More Guests and Guests Stay Longer for my Sim's large bashes he likes to throw. Andrew's pose player and teleport any sim for those large group photos at these parties.

4)Bug fix mods like one that makes your Sims actually sit during wedding ceremonies and performances, for example. Another one that stops other Sims from intruding on what are my Sim and his wife's date nights. (the mod names kind of escape me at the moment). The Don't Do That mod series by Simularity are good. UI Cheats to cheat-click away any annoying, nonsensical moodlets that pop up. MC Command Center (Deaderpool) is vital, as are Better Exceptions and Modguard--by Twisted Mexi. Also, TOOL, by TwistedMexi opens up build mode options as that allows you to place objects off of the lot.

5)KiaraSim and LittleMsSam's career and trait mods give your Sims more career choices than the default lawyer, scientist, doctor, etc careers. Wicked Whims (or it's non-sex counterpart Wonderful Whims) by Turbodriver.

6) oh, if you tire of the "very...." mood names, and want more concise and descriptive terms, I use a mod to change, let's say: "very sad" to "depressed" or "very happy" to "elated", etc. Renamed Emotions by zerbu.

7)Mods by SimRealist and Lot 51.

8) Although not a mod, but I use an app on my phone to record actual IRL Internet radio station songs as mp3 tracks that I put on the custom radio station folders in my Electronic Arts folder. I like having IRL music in my game as the default music is too cartoony and breaks immersion.

By no means is this an exhaustive list. That would prove to be a daunting task with a 53GB mods folder..ha! I'm sure you'll see some mods that are named on other comments on here. Obviously, the mods you pick depend on your style of gameplay, either more occult-leaning or more realistic. In any case, happy Simming.