Baby blankets make a great baby shower gift, but they take a long time to make. Good thing I love knitting!
I have never tried knitting.  I read that a garter stitch is an easy one to start with.
Yes that is true. You should try knitting flat things. It's when you try to make hats and other circular things that it gets tricky.
Would a stitch scarf be something good to start?
Yes, scarves are very easy because you don't have to make them too wide. You can use regular needles as opposed to circular needles. 
Are straight needles easiest to start with?  I see that bamboo is good too.
Yes straight needles are definitely the easiest. I don't think the material of the needles really matters though. You can get bamboo, but plastic is the cheapest.
Can I get a good set at WalMart?
The selection at WalMart is just ok. I would recommend going to Hobby Lobby or JoAnne's fabrics instead.
What things should I look for in a good pair?
You should know what kind of project you are working on first. Are you going to start with a scarf? If so, how wide do you want it to be?