For mobile data, if you have access to immobile data at home and work, 1GB is reasonable if you're not streaming while you're out.
The people who are downvoting you must be terminally online.
Like you, I use wifi at home and work. My mobile data use is typically around 150MB/month.
There’s a massive difference between “terminally online” and “goes out of their way to avoid using any of the capabilities of the technology.”
If I’m paying for a 5G connection on a phone that’s more powerful than the computer I owned 5 years ago you’re damn right I want to watch my dumb video in 4K and stream my music lossless.
Not downvoting, but any typical online activity during commute or while travelling will blow through 1GB. Music every day, or a video once in a while…
I also have WiFi at my usual hangs, but thus far this month I am on 15GB of my 50GB monthly plan. Sure I could pre download music or videos to watch, but it would be much more of a hassle. And some sites, like twitch, don’t really have an option to download.
The biggest problem is modern phones gobble up data even if you're not doing much. All that background app activity and notifications aren't cheap - what do you think they're doing back there?
If you install GrapheneOS you'll notice your device battery nearly doubles, due purely to less network permissions and less background activity. I wouldn't be surprised if mobile data usage drops off, too.