Any good tips on what kind of sturdy but yet not so spendy cake boards to use. And a good covering?

I think foamcore is about the cheapest you can get. Just cut it to the desired size you want (I use a hot exacto knife). You can pick up the foamcore at most office supplies stores, Home Depot, etc...

For covering, there are plenty of foils made for covering cake boards, but I prefer to use fondant, royal icing, or fabric covered in contact paper (I've heard others say contact paper is not food safe - but I use it).

Thank You!