Seriously go to the tutorial, and read up on everything there is to know on junctioning, and GF abilities. If you're in that situation at this point, there's way too much to explain to you in one post.

Also check out the FFVIII section and walkthrough at www.eyesonff.com. It'll tell you all about juntioning, and what magic to junction where.

Quick hints: Stick Meteor on Str-J and upgrade your gunblade to Lionheart. You can stick Ultima on Str-J for even more strength, but that's more useful on Elem-Def-J.