Welcome to the forums!
It's great to hear that the scene modes are working well for you, and if that's giving you the creative control and results you want, fantastic. Be aware, though, you can unlock much more creative control by using the P, Av, Tv, TAv and M modes - but there's a learning curve involved.
Regarding lenses, the DA35 f/2.4 and DA50 f/1.8 are the only low-cost prime lenses currently available. However, the HD DA15, 21, 35 Macro, 40, 70 and 20-40 zoom Limited lenses are all current models, and each one of them is superb (the Limited designation pretty much guarantees this). There are many other current Pentax and third-party prime and zoom lenses that are compatible with your camera too