Well, really everything depends on what you want to grow.

My usual advice is not to spend too much on heating unless you have a clear reason to do so.

But in your area you ought to be able to get a very early start on spring (Feb) by growing cool weather greens and starting seedlings, even without heat.

I thought that I would start with some onions, green onions and garlic, maybe some carrots or would it be best to just wait until Feb or Mar to start these?

Excellent!
I think you can try starting all of those now. I grow carrots and green onions through the winter. They won't do much in Dec-Jan but they will spring into action after that. Give it a shot and report back!

Along with my boxwood, leyland cyprus's, and spider plants, I fell into a source for windmill palm seedlings. Currently have 120 potted and am going back today for 300 more. In a couple of years or so, I hope to have quite a wad of them!!