First time dry wall question

I framed my basement, everything is level/plumb as far as the frame is concerned; however the rest of the basement is not. Floor is cement and a little uneven. There is already a sheet rock ceiling from the previous owner. Which is uneven. I have never done drywall before. I've read books and watched YouTube vids and am comfortable with what I'm doing my question really is this: in 2 spots I'm going to have small gaps between sheets. 1 gap is about half a centimeter, the other is along the ceiling and is just shy of 1 cm. for something so small, can filing that with mud do trick?

This job doesn't have to look perfect, and I'm not against throwing crown molding up if I have to lol. Just looking for suggestions. Thanks everyone.

 

After drywall is hung, standard procedure is to prefill any large gaps... there will always be a few. Generally I will mix up a pan with some powdered setting compund, like Easy Sand 20. It dries fast and is harder than joint compound, less likely to crack.

Once gaps are filled, you then tape and finish the drywall joints as usual.

 

Thank you much for the quick reply.
Enjoy your Sunday!

 

Is the ceiling finished? textured? Generally you tape the joint between the wall/ceiling but sometimes it's prudent to just finish the wall and then use molding to hide the gap/crack between the wall/ceiling rather than have to bring fresh mud onto the finished ceiling.

It's better to apply thin coats of mud than apply it too thick and have to do a lot of sanding!
btw - welcome to the forums!