Threadloctite , gasket maker or thread tape

[cors]

Can i inquire about the do's and dont's of using Loctite type , gasket maker or thread tape when dealing with gas pressured thread connections?
Is there a general rule?

[rossko]

Avoid whenever possible due to risk of debris entering system. Use liquid PTFE on tapered threads, use new olives dry on compression joints, make new ends on copper pipe for dry flare joints.

[cors]

I looked everywhere for some fittings and with my limited knowledge in Russian i could only scrounge this set up in the pics.
I visited 4 stores and most of them did not have a way to do but one guy sold me these.
Will this join work or is it totally in correct?

[Gilbertd]

Looks spot on to me as long as the olive is the correct size for the pipe.