Since you need to know about 6 traits to make the really good sets, and more traits for some of the powerful Niche sets, don't sweat learning "bad" traits. Reason, your going to be learning most of them anyway at some point, whether you ever use them or not.

The key is to learn one trait on each item, then the second, then the third. You can limit this at first to only items you would ever make, like Light Armor for your Casters as an example.

Following is part of my Crafting Leveling blurb:

.........it takes 6 traits known to be able to make Hundings or Julianos, 9 Traits for Twice Born Star. You don't need to know these traits on everything, but you do need to know them on the items you will use. So, start learning those traits. Focus on the gear you will use first, then fill in the rest later. This means:

Casters
Heavy Chest/Legs
Light Feet/Hands/Waist
Shoulders and Heads are good to, but there are 2 Piece Monster sets that can take up those slots. So learn the traits on these pieces, but prioritize the ones above.
Staves (all 4 of them)

Stamina
All Medium Armors
Daggers, Swords, Bow and Shield

Learn Training, Divines and Infused on the Armors first, Sharpened, Precise and Training on the Weapons. Powered is good for the Healing Staff, Defending is good for Sword or other one handed Melee. Then fill in the rest until you have 6 or eventually 9 traits. Some people recommend Nirn as an early trait to learn. Unless they change it, don't listen to them. You might use it on a Shield or a Weapon but that is about it. You need it someday, but it's expensive and you need your gold for other things.

Invest the skill points into the Research Passives. I can't stress enough how much of a time sink Trait Research is. Be able to learn more than one at a time, and reduce the time needed. Get an addon for Trait Research Tracking, I recommend Craft Store. If your on the Consoles, find one of the spreadsheets out there or make one to track this. Have I mentioned you need to learn your traits?

Doing this you will be ready to invest skill points into Crafting when it matters and not have to spend months getting ready. Did I mention Trait Research and how much a time sink it is? The last two traits will take you a month each to learn, on each item you learn them on. Get started now, yesterday would have been better.