I would say Mage Hand and Ghost Sound.
Mage hand is forever useful for many things, from using it to wrap a sash around your opponents legs during battle, to getting a dagger to a party member who is weaponless and out of spells to (if your DM allows) grabbing the potion bottle that your enemy is planning on drinking from to heal himself while you are fighting. For a 0 level spell, when used creatively, you can get a lot of of it.
I've used Ghost Sound many times to make opponents think that they were about to be attacked from the other side. (IE. they hear voices coming from the other side of the forest and go to investigate while we loot their camp). I'd just call this one Voices.
I also use Detect Magic a lot. Just keep in mind that this takes a few rounds to kick in.
Prestidigitation can be useful for flavor mostly (ie. I make my food taste a little better..., I entertain the crowd with my tricks and earn a little extra coin). I haven't really used it much for anything else.
Mending can also be useful, if you see a need for it in your parties structure. Do you often need things to be mended? Same with Light. Does anyone in your party have excellent low light vision? Is finding other means of light often hard for you? Cure Minor Wounds is another one, but if your party has a wand of healing, or another healer, it might not be worth taking.
I would say really, take a moment to look at your party and what sort of situations you often get into, and what skills your fellow PCs already have and choose from there.