In addition to what Wkw mentioned, you could also make urns and perhaps even sell them for a nice profit. It can be a rather tricky and illiquid market to navigate last I checked. If you are going to do some sort of jewellery, doing it on a portable crafter can offer benefits, most importantly including additional XP. If you join the friends chat 'portables' and ask you may find an F2P world on which someone is placing them, typically at the Combat Academy in Lumbridge. Cutting gems will be much faster but in general is a large loss in GP.