inzendium

No Mycosynth Golem in an artifact affinity deck?? I mean, this isn't actually affinity (aside from Thoughtcast), but Mycosynth Golem would still make getting things out much easier. If you do add that, maybe a couple high-cmc cards would be nice (Platinum Angel, Platinum Emperion, Blightsteel Colossus, Darksteel Forge, etc) Also, Mycosynth Lattice would help if you actually want to reinforce Affinity. These are all just suggestions, and if you don't want to add more affinity stuff, you can probably ignore them (except Mycosynth Golem, as he helps tons to get out artifact creatures even if you don't have other affinity stuff)

Talk about an infinite budget. For more recurring creature protection, maybe add an Isochron Scepter and pair it with Tangle? Pretty interesting combo (Blasphemous Act + Repercussion).

First thing that immediately jumped to my mind was Chromatic Lantern. It is great in any rainbow deck but especially here, since it is excellent for the Door. I would swap 2 Propetic Prism for 2 Chromatic Lantern.
Second, I would add more land. Even if this were a 60 card deck, 24 land is a touch low for your mana curve. Seeing as this is an 80 card deck, you are going to want more land than usual either way. I would fill in the land gaps with basic lands, since with only Guildgates you will be constantly playing a turn behind your opponent. Don't get me wrong, having more color options is great, but if you're aiming for more colors per land, you might go all the way and get some tri-color lands (Arcane Sanctum, Mystic Monastery, Crumbling Necropolis, etc) or even something like City of Brass or Mana Confluence (any color mana per tap at the cost of 1 health per use).
Speaking of the guildgates, you may want to switch them for the newly released dual-color lands ("When ___ enters the battlefield, you gain 1 life") although if you don't want to take out Gatecreeper Vine then guildgates are likely better.

I play a rainbow deck myself and these are just some suggestions I thought of. You didn't seem to have an issue with budget, and the cards I suggested are fairly low-cost anyways, but again, they are simply suggestions.
Hope I helped! :D

BONUS: In reference to the City of Brass suggestion, City of Ass is a funnier and safer version (but it can't be used in any sort of tournaments). Also, City of Ass is slightly more expensive.

That's a good candidate. Holds them on the ground while they watch me tower over them.

I'm pretty happy that this combo actually works well. It seems good on paper, but I don't know how well it would function if you put it to use. In fact, one of the reasons I started to like doing combo decks was because I saw your Stuffy Doll self destruction deck. I ordered that a while ago and have made a couple edits to it (Pariah, anyone?), and I have loved making up card combinations since. Thanks for the inspiration :D

Maybe a Master Biomancer? He just gives more strength to your creatures and increases opportunities for evolving.

Also, I don't like to advertise, but could you take a peek at this mana ramp I thought up? Thanks in advance.
http://www.mtgvault.com/inzendium/decks/sasaya-what-now/

I just realized Kozilek's Inquisition is also expensive. I also didn't see the price of Death's Shadow and I think I will swap him for Jokulmorder.

I threw in some Kozilek's Inquisition and Duress, and some Dimir Machinations to transmute into Buried Alive (Thoughtseize, the tutors, and Entomb are all a bit out of my price range). Go for the Throat is also a great kill card. Thanks for the suggestions!

I would be playing this in casual. I don't want to devote much to discard, but I think a few Thoughtseize wouldn't hurt, to deter counterspells.

I don't know why I didn't realize Worldspine's ability; I even have the card myself. Thanks for pointing that out, though. Is there anything I should add to make grabbing Exhume and Buried Alive (and Dark Ritual) easier?

I don't think Ugin fits into this type of deck mainly because of his mana cost. Also, did you mean to enter mountains instead of Dwarven Hold? Because you can only have 4 of those. Lastly, I really don't think 16 land is enough for a 65 card deck. Maybe it does work out for you, but I would try to push to at least 20 lands (lots of mountains).

Lightning Bolt is just a better card than Lightning Strike, now that standard is no longer a goal.

I forgot about Sigil of Empty Throne. That card is a beast in this deck. I will make sure to add that. Thank you

While I also think Visitor is the best, the other two are very good in certain scenarios. In this situation, I agree with eap5000 that Lord of Innistrad would be a better choice.

Venser, the Sojourner could be fun. Use his ultimate and exile their stuff (particularly lands) every time you cast something else.

Okay, this combo might not actually come into play, but Sunbond to put onto Sage of Hours, and then Ajani, Mentor of Heroes. If you are able to use his third ability, you get 20 extra turns, which you can then use to spam +1/+1 counters and use it again. Plus, every second usage (or even every usage) of his first ability can trigger an extra turn, making hitting the third ability faster.
WAIT! THIS IS BUDGET!
Darn it

Added Unmakes and Silent Sentinel for tossing enchantments back onto creatures. I sideboarded Felidar. Maybe I will throw him in, but he is just a bit out of my reach for now.
Thank you for the suggestions :D

Good idea. I couldn't really think of anything to put in for split lands without making it too expensive.

You could toss in Pariah's Shield to toss onto Stuffy to make them take damage they try to hit you with. Plus, more benefit for Mycosynth Golem.

I hate to advertise, but could you take a quick peek at this life gain deck I made? I would really appreciate any and all feedback I could get.
http://www.mtgvault.com/inzendium/decks/so-many-lifelinks/
Thanks a bunch either way.

Oh! Increasing Savagery would be great! One extra turn for four mana, then two extra for seven mana! That seems like it would be pretty good.

EDIT: Damn it! I keep forgetting this is standard! My ideas never work >:c

Two reasons why I want to keep Hover Barrier:
1) The high toughness works better with Phenax
2) Even with Fog Bank/Gomazoa's ability, they don't stop trample, and they have low toughness
Thanks for the suggestion, though. Still very much appreciated.