1. buy raw mats and consumables on weekends
2. list them at 6pm on raid (er Ops) nights
3. profit
It really is as easy as "Buy low, sell high".
You can make mountains of money just by kowing your servers economy. Know what sells and when. Learn to recognize price trends, cycles and shifts. Reading upcoming patch notes the day they are published can also be a big help.
Use your 3 skills to make whatever you want your character to have but realize crafting isnt the answer to more credits. For 3 out of 4 people, crafting will be a credit sink.