Since Orvar optimizes very well as a low-cost deck, I figured I'd try to throw together a budget version... hopefully keeping it under $100.  It helps that Orvar doesn't have a ton of nonbasic lands to include, and the ones worth copying aren't expensive to purchase.

Nanogene Conversion is gnaaaarly in this deck!  For four mana you turn all your creatures into nonlegendary copies of Orvar, then cast one spell targeting one of the Orvar copies, triggering all the other Orvars to make a copy of it.  Say you have eight creatures and Orvar... well, now you have eight copies of Orvar, plus the original.  At the end of the turn, the Nanogene copies turn back into their original creatures, and you still have eight Orvar copies ready to get downright oppressive!  Cast another spell targeting a nonlegendary Orvar copy to basically double the number again... it's just not fair.

Faerie Artisans is an awesome Orvar card, because you can make copies of the copies it makes, allowing you to copy any new creature an opponent has, right after it enters play.  Not to mention it would nullify the -2/-2 of an Elesh norn drop, then you copy it and take the upper hand!  lol  It's a fun card in general, but it dominates in an Orvar deck.  Metamorphic Alterations has a similar effect... cast it targeting an opponent's commander, turning it into a different creature on the board.  Then just make copies of it, turning each opponent's commander into something relatively useless, or turning one of your useless creatures into something much more beneficial... it's a huge board-control option, and only 2cc too!

Blade of Shared Souls is a fun Orvar card, because with blue, in general, but also in the scope or Orvar synergy, when you copy a creature, you either make a token copy via a spell, or you cast a permanent that becomes a copy of it.  The problem with this is you never end up with a permanent that Orvar can copy and target new objects with... you're always stuck making copies of whatever that card originally copied.  Blade of Shared Souls changes that... it stays an equipment that you can copy, which then creates a new creature that copies a different creature you control. Now, understandably, one might ask "why not just target the creature you want to copy, and copy it with Orvar?" and this is a very valid question.  The thing is these are equipment, so if the creature they equip dies, they remain in play, and can be re-equipped to copy other creatures again, requiring artifact removal to get rid of them.  On top of that, and this is the fun part, you can equip them to opponents' commanders that you steal... talk about salty...

Backfire is an interesting option to include... once it's in play, your ability to copy it at instant speed to enchant an opponent's attacking creature will quickly slow down threats that deal too much damage, as well as using it to equal the playing field with something like Kediss, Emberclaw Familiar.  But is it good enough to make the deck...?

Narset, Parter of Veils works really good in here... not only does it limit opponents' cards draws, but it replenishes itself, so to speak.  This deck has 27 targeting instants and sorceries, so on average you draw one every four cards.  Narset lets you filter out one of these cards (out of four) twice, before needing to be retired.  So you cast Narset and -2, then next turn to -2 again, bringing it to 1, then target it and copy it with Orvar, replacing the old one with the new one (legendary rule), then -2 that one before the end of your turn.  Each of your turns you get to use the -2 twice, typically netting two instant/sorcery spells, for the cost of using one such spell to copy Narset.  She effectively replaces herself.