Flax. At your level flax is always good to stockpile and sell for some small, incoming funds. And when you get higher, collect soil as well. Particularly the grade 3 soils. Those sell decently enough as well. At 50 you can also start getting clusters (fire/water/wind/etc). Selling those in bulk can be pretty lucrative as well. Granted this all depends on your server. Oh, oh! And logs. Logs sell well as well.

Good luck!