Think that's mostly up to you know that's not the best answer but there are a million and one different training guides and plans out there and a lot of them directly contradict each other. If your happy with what your doing so far I would stick to it and do easy runs Oh and for shame no such thing as a easy run by the way, Think on it could you have done what you can do before you started the 5k program? Give yourself some credit and a big

Speed work is very useful but I wouldn't think to much on it unless you start ramping up distances of say 10 miles or more. The benefit it's going to give you before that sort of point will be very minor.
If your fancing doing longer races through worth taking a look as it's good to get into the habit before you start doing the longer miles and let your body get used to it.
If you have a club near you might be worth while saying hello and working out if they are for you. Like most things there are good and bad clubs out there and some can be a little clicky but most are great and friendly.