Yes, you will need to meld materia into your gear. For melding gear that requires crafts you don't have at 50, you will need to ask for help from crafters who do have those crafts leveled. When you target another player, one of the options that you are given is "request meld" - this will allow you to set up a materia melding window, but lets the other person do the actual melding. That is how you meld gear that you can't meld yourself.