Join a Free Company that has Material Supplier house merchant, if you haven't already. The Materials Supplier has 90% of all crafting mat you will need below level 20. The sales price from Material Supplier is a small fraction of the price on the MB. And, you do not need to spend time gathering.

You will, as other have mentioned, want to level your gatherers, as they will enable to you obtain mats above level 20 with only a small time investment.