Be careful with a 3/32 gap. Some places will not allow you to use a grinder on the test and it will close up on you.
First thing you want to do, find out what the QC wants. Then go from there.
Second, everything depends on the size and thickness of the pipe being welded. Normally, I like to start off with a 3/16 gap using 1/8 filler wire. By the time you weld up half of it, you will have to go with a 3/32 filler wire or I turn the heat up a bit and stay with 1/8 and let it just fall in.
On the purge, I like to use a gas lense at one in, tape it up real good and tape the other end completely and then poke a couple of holes in the tape. As you close up your joint, the excess purge will escape out of those holes and not thru the root bead.