0.8mm wire, Argoshield 15, new tips, new shroud, SHIT LOADS OF PRACTICE!!!

Plus as already stated, make sure the metal you are welding is clean, not just on the side you are welding but on the underside also. If a butt weld is not needed make good use of mig-plug welds, basically two layers of metal overlapping with a hole in the top layer, ensure both layers are clamped up tight to each other then weld to the under layer through the hole and fill in the hole.

Get a decent mask, one of the self-dimming type.

Oh, and PRACTICE SOME MORE!