Nah, you definately don't *NEED* any upgrades...but they would help. However getting lvl 3 upgrades before even getting any "Creatures" would be silly. General rule is you don't get upgrades before you get a good amount of the units. However you can always do as you wish
You might get a graveyard after you get your bone yards, or if you sell an ankh or item you got from red creeps...but the graveyard and especially the upgrades themselves just slow down your inevitable production of frosties. Also if you end up spending wood on upgrades, it will delay your tech considerably.
I don't get gyard in my build...but feel free to do so of course...