This video does not go heavily into crafting just yet. That will be later on. As you quest and do activities, you will stumble upon a bunch of 7*-9* weapons and units along with a various amount of photon discs and technique discs. You want to take the level 11 discs and desynthesize them. You can do the same for units and weapons.
You can desynthesize those of a higher grade like 10* weapons or units, but I highly advise against this UNLESS you need the materials for extending with the special extending bonus. I will have a video about this for the next set of tutorial videos.
For now, start desynthesizing and getting materials so you won't have to buy it in the player market later. DO NOT BE LAZY! This will help you with someone's certain cilent orders.
A link to a guide talking about what units and weapons would give:
http://pso2.cirnopedia.info/craft_4.php
Still outdated, but it gives out a good thorough breakdown on what gives what.