In a nutshell, keep writing! The more you write, the more you earn! Also, it might be worth trying some SEO keyword research to find out what hubs there is an audience for. I must admit I'm very bad at targeted SEO, and my good traffic hubs came about more from luck than anything else. Some people do well from SEO though, so it is worth researching a bit.
As to whether Hubpages is worth your time, that depends on what you value your time at, and what would make it worthwhile. You are unlikely to make a fortune, so if it is only worth it for you if you are make hundreds of dollars a month, I'd probably stop now (not saying this is impossible to achieve on here, just that it will take years of hard work and a lot of luck).
If you are happy to dedicate a few hours a week regularly, don't mind if you don't get a payout for at least 6 months, and a medium term goal of $50-$150 a month is acceptable to you, then carry on!
My view is that you should write on here because you enjoy writing and see the money that you earn as a bonus (albeit expecting that given enough time and effort, you will get some sort of bonus). And don't give up if your hubs don't get much traffic at first, as you write more hubs your overall hubpages profile increases, both within the site and especially from Google as they uprank you. Hubs do generally age well, and will get more traffic the older they are, assuming they are still relevant and up to date. I wrote about 30 hubs, decided it wasn't worth it, left for 6 months, and then noticed I was starting to earn some money on the hubs I'd written, so came back and have been on here since. I kind of wish I hadn't had that break now, if I'd kept faith I'd be earning more!