Generally speaking, I think you better save your gems. Not really must open. On other hand, statdust Dragon (and with it's corresponding box) is a better choice to invest. General speaking.
Spent 16800 gems, still don't have 100% complete decks. Only 1whirlwind, 2consonance, 1sakuretsu, 1BWD, 3vajrayana.
So far I feel that it's not optimum without 3 consonance, also has no useful lv 8 synchro (which is very easy to bring out through this deck). Farming gems to draw stardust now. Don't really mind about x-saber/ blue eyes. Just stardust + some general support eg galaxy serpnt,dai,etc
This deck is dragunity. It isnt based on summoning stardust but yes u can never go wrong if u have a stardust in ur extradeck. Sometimes u just need a lvl8 synchro and right now stardust is the only available option.