I think I might have the qualifications to answer this one... There is plenty to do on F2P, although of course most training is naturally slower. If you fancy PvM you can take on revenants in the wilderness - one of the more thrill-seeking activities that it has to offer. You can still get a rare drop from them once in a while worth a good chunk of money. Dungeoneering is a great activity (at least in my opinion) to engage in. You can see how fast you can complete floors or work toward some gravite weapons (for the most part, the best in F2P). You can do it solo or in a team, whichever you desire. Then there are more AFK things like cooking, firemaking, or even crafting some jewellery or smelting bars for profit. It kind of depends on what you like doing in general too though!