There are many obscure items that can easily make a tidy profit. Many are quest items or herblore seconds ex: spiders eggs (~600gp), Limpwurt root (~2.2k), Red dye (~1.7k). I would look for these types of items through the grand exchange price change page. Gathering most items like the above do not earn you exp

Also tied to the G/E is item 'transformations' ex: untanned dragon hide to tanned, seaweed to soda ash. There are also a few tasks that can earn you slow exp while making money ex: flax to bowstring.
Best of luck with your first month
