I've been growing Germidour for a couple of years, which has done well. It over-winters up here in the Pennines (where it's reliably cold and wet...), and is a nice mild variety.
As imcg says, you really should not try to preserve garlic in oil at home. Commercial producers have to put preservatives/acidifiers in, as botulinum is unnoticeable, and potentially fatally toxic. There are other ways to preserve garlic, but in oil isn't one to try at home!
With regard buying growing garlic, rather than food garlic -- food garlic may have been treated with chemicals/etc to prevent it sprouting (ie, to store it longer in the shop), and may not grow as well.
I can also recommend elephant garlic, which is great fun, and produces huge mild cloves!