The inside of the sampling tab in version 3.0 is as shown in the image.
If I set the "max sample size" to 4096, it takes a very long time to render. how should I set the sampling tab?
You can set the Time Limit (just above the Denoise option) to something you like. Then you can leave all other Settings as they are now, or try to change (some of) them; the actual render time per frame will stay within that limit. (Plus a bit more for saving and "synchronization")
Btw, is that the official 3.0 ? Because when using Adaptive Sampling (Noise Treshold), Scrambling Distance and Pattern should be greyed out:
Forget that last remark, you don't use a Noise Treshold in the Viewport, that's why those things aren't greyed out :)
The Settings in the Render Tab are pretty advanced and take a lot of experimentation and there are no 'Best Settings'; it is mostly a compromise between time and qualtiy and then also different for different scenes and can even be different for different hardware. But this (relatively new) Time Limit is very handy. You can even, if you want to render for, say, 8 hours an animation with 250 frames, type in: 8h/250 and it will set it to the correct time (pure render time only). Then test 1 Frame to see if the quality is acceptable.
Also, I don't know if this is mentioned in this course, for animations it is helpful to use a different Seed per Frame:
