The Fantastic Lumix G7

OK, a couple of suggestions (that some people already gave):

1) For low price and amazing performance I think nothing beats the Lumix 25mm f1.7. That lens you can constantly find very cheap I already compared it to the 25mm f1.4 and the Olympus 25mm f1.8 and I think that it is just at the same level or very close to those (and on some specs, like silent and fast focusing, even better);

2) For amazing quality and look and a little more "wider" view for landscape, the Lumix Leica 15mm f1.7 is just awesome. I much prefer it to the Olympus 17mm f1.8, mainly because it is wider so it is more useful for landscape, but the Oly one is also amazing.

3) For a low price versatile and light weight solution, the 12-32mm f3.5-5.6 is just a gem! So tiny, but at the same time you have all your bases covered: amazingly handy focal length, OIS, quite sharp (perfectly sharp for video), wide (24mm equiv at the low end), etc. Awesome lens!

4) For a very fancy middle ground between prime and zoom, the 12-35 f2.8 is just my favorite lens ever! I know it is more then your $500 budget, but, you can easily find the V1 used for around that price. If not, you can also look for the Oly 12-40 f2.8 refurbished or used very close to that price.

5) My favorite prime of all times EVER is the Lumix 42.5mm f1.7. I use to have a Canon system and the EF 85mm f1.8 that I loved, but I think the Lumix is FAR better. But, I know it is very portrait oriented and not so useful for the things you want (street and landscape), so, even if it is my favorite piece of glass, I don't think it would be that useful to you

I hope that helps!