You'll find things have vastly changed. For starters, sick to fighting mobs much closer to your level. Equal or + 1/2 levels.

With the new gear, many people are focused on making the higher end gear at the moment. Smart crafters will sell gear for lower levels and make a decent profit. They just have not realized it yet. You might have a tough time finding gear just yet. Many materials can be farmed though and you can ask someone to make the item you need.

You can only pick up 8 Guildleves at a time, once you use up some leves go back to the counter. You will find you can take more of them right away.

Materia, there are a couple quests you should start. In Ul'dah there is an NPC wearing something close to chefs gear, speak to him and he will send you on a quest to Deliver items to a Goblin named Mutamix (forget the spelling). To find him head out of Ul'dah and head north towards the first Camp. You will see coloured smoke in the sky, head to it. Here you will find a small camp with NPCs to talk to, which will allow you to start converting Items that you have Spiritbonded. Keep in mid that you need Catalysts in order to actually add materia to gear.

Dated gear can become materia, but it can not have materia added to it.

EDIT: and renshi beat me to it while I was typing this up.