Unfortunately you need the correct corresponding craft to meld materia. Like you said, gsm for jewelry, weaver for cloth armor. The crafter level must also reach the level of the item in order to meld. So for instance a level 30 gsm would not be able to meld into a level 60 jewelry piece. If this sounds like too much work just shout out that you are looking for some melds. Say the level and craft and you should be able to find someone who can do it for you. You'll probably need/want to tip them. Good luck