Please pay attention to mana curve. By mana curve, I mean you want to have things to do each turn for turns 2 and above. For example, take a hard look at your stuff in the 4 mana slot and above. What are dead cards in games? Drana, Liberator of Malakir and Phyrexian Arena will lower your mana curve and produce desired results. Also, look for ways to help get your lands on each turn or early: Gatecreeper Vine , District Guide , Caravan Vigil , Rampant Growth may help.

This deck runs 12 cards that ramp to help jump the curve plus another 7 that make a ridiculous amount of mana after proshh is out. Getting to cast the spells isn't much of a issue tbh. The ramp cards you mentioned really need to put lands straight into play, them going to your hand doesn't help skip ahead to play the bigger more impactful spells.

I'm listing the following cards because they are too slow, don't do enough, or there are better versions. Let me know if you want me to elaborate more. Crop rotation, shared animosity, in the web of war, earthcraft, dragon tempest, decent of dragons, cryptolithic rite, ophiomancer, beastmaster ascension, and Endrek Sahr. Could even cut a land if you wanted. May actually need a few more mountains to get enough value from Valakut. Let me know if you want me to explain a pick further.

I can see why you said Crop rotation, shared animosity, in the web of war, dragon tempest, decent of dragons, ophiomancer, and Endrek Sahr. Dragon Tempest & Decent of dragons are more pet cards than anything else.

The other 3 cards are just plain nasty with prossh, not sure why you mentioned to cut those. Mind explaining your reasoning? If you havent tried them before, they have just flat out won me games, especially Earthcraft allowing me to cast prossh multiple times in 1 turn to just kill everyone!
Beastmaster Ascension
Cryptolith Rite
Earthcraft

I took a look at your deck and its themed on stealing creatures to use em and sac before they get it back, allot of fun and even funnier when you see the salt building on your opponents! I used to run more of those effects with my old playgroup but the guys I play with now are more combo/spell sling focused so stealing creatures doesn't really do anything impactful anymore.

I misread earthcraft, so that's my bad. My opinion for the other two is that you are forced to untap with Prossh+tokens. It also telegraphs your big play, and has the whole table looking at you.

The threaten cards are only for control so I can set up my combo pieces. Also slowly ticking people down with their own creatures is a great diplomacy tool. It also allows me to switch in Vaevictis Asmadi, the Dire for less spikey games. Thanks for the upvote. I got you back.

I used to make the mistake of playing beast master before prossh, that just had people on standby to remove it. Now its always in hand until the tokens are able to attack and swing at the person whoever cant stop it.

Vaevictis Asmadi, the Dire has been such a fun card to play, not compettive in a Prossh build, but holy is it sweet when you drop it down with haste.