I second what Emaemmaemily said. You need to be quite careful with staffys as they can have an aggressive nature, its sort of what they were bred for. Some are really lovely, but I've witnessed some really nasty ones as well. The fact that it's a rescue dog as well, might give it other problems you might not be prepared for.
A staffy attacked my dog at the park years ago, he ran away and suffered from some nasty injuries. He became really scared with other dogs afterwards. What makes it even more disastrous, is the owner actually released it on our dog, and was laughing, when it was attacking us! I get scared a bit now when I see one and always try to avoid.
But like I said above, some can be really nice as well. So I don't want to completely put you off the idea. You just need to look into the history, and also observe how the dog acts with you. If it's nervous and avoids any contact, or worse, seems aggressive, I'd highly recommend looking elsewhere. If it's outgoing, and likes people then it should be fine, especially if its got a good history.
I think Labs are a good choice as well. We've now got a LabxCollie puppy, he was so easy to train, and has a lovely temperment. Most labradors do have a good temperment. I recommend a cross breed, for the same reasons above. You'd need to do your research on both breeds, and possibly the temperments of the parents. If you get a rescue dog, its really important to try and find out their background. I would personally try and avoid a dog which has been mistreated, at least for your first time.