Okay lets go with Staves since you play a human mage. Lets upgrade one for you. Find a staff that has empty Grip and Blade slots on it and use that for this.
Make sure you have a schematic for a staff grip and a staff blade. use the Weapons crafting machine and click on the little picture of a staff in that window. Find a Staff Grip Schematic you have the materials to make, then find a Staff Blade you can make.
Notice how choosing different materials affects the stats of the item you are crafting.
Once you get them made, go over to the small bench and click on the UPGRADE Weapons side.
Find your staff in that window and click on it.
Now you see the slots for the grip and the blade.
Click each item there to choose the upgrade to apply.
Over at the right see how the stats of the upgrade piece get added to the staff.
Armor works the same, just use the armor crafting table to make armor upgrades and, the Weapons station to make runes, then follow the same method to apply them.
To upgrade companions just select them instead of you at the upgrade table, same as adding abilities when they level up.
Don't feel bad, a lot of RPG games don't have crafting. And actually I have only played 3 RPG in my life. The Dragon Age series, Rift and, The 4th Coming. Those games all do have crafting so, it's a familiar mechanic to me that I just need to figure out the details of for each game.
Level 20 is pretty good, 27 is the cap so, you're close. And yes there is plenty to discover in the game. I usually play a mage as well - Inferno with the Knight Enchanter specialization or, the Rift Mage specialization, depending on if I am doing a solo run for that game or, using a party. There are other guides online, Dragon Age Wikia is one of the better sites but, this one might help you too DAI Maps and Walkthroughs