Here's a horribly generalized, bound to insult many people, but still relatively accurate stereotype: there are 4 good neighborhoods in oakland, 3 of which are affordable. The oakland hills are very nice and very expensive. The three affordable neighborhoods are around jack london square, around lake merritt, and around college ave near the berkeley-oakland border.

Rockridge is safe, but more expensive than the rest of Oakland. I was paying 1700 for a one bedroom in a duplex. I recently moved to Adams Point and it's nice, I actually feel safer walking around here because there's always people around, and it's much livelier compared to Rockridge, and we were able to get a larger one bedroom for about $500 cheaper.

It's been a while since I lived there myself, but the areas next to Lake Merrit and Jack London Square are very nice and generally quite safe. My brother used to live in Lake Merrit until last year and loved it.