I'm not a fan of that DSLite wallet case, it would look like you were carrying around a purse.
Agreed. The less it looks like a purse, the better. I opted for this case:
It's small and protective, and has pockets for DS and GBA games. You can even use the elastic strap inside to keep the DS Lite inside the case while playing it, but I haven't bothered doing that.
Also, I bought the Hori DS Lite screen protectors when I got my Lite. I put them on very carefully and exactly as described, and they both still had air bubbles underneath that I just couldn't get rid of. They don't fully cover the screens either; there is a small space all the way around the outside and it looks really silly if you can't center them perfectly. I peeled them off and never looked back.
I have been using my Lite daily for over two months and have absolutely no desire to get a screen protector kit. It just doesn't need it. Besides, the actual screen surface is underneath the plastic screen cover; the screens already technically have screen protectors on them. No point in getting a screen protector protector, know what I mean? I only have the tiniest little scratches (which all DS/GBA screens inevitably get) and you simply cannot see them when the backlight is on, no matter how hard you try.
My advice? Don't waste your money on a screen protector kit.