Hey there!
Well I don’t have a lot of advice on the mana base since I’ve never made a five color deck before. But I always though
Transguild Promenade would be a good choice for five color decks. Sure it’s a bit of a tempo hinderance, but I don’t think it’s that much worse than a
Karoo land and it gives you access to all 5 colors in one land. (Also, it’s super cheap to buy)
I understand that this is a political deck, but I still think you want to add some removal. Part of a healthy game is removal, especially when you're facing down a turn four
Terastodon off of your
Braids, Conjurer Adept. You might want a
simple Counterspell to stop a player mid-combo. (You can even go with more "friendly" counter spells, like
Dream Fracture or
Arcane Denial.) Plus if you want this deck to win you can't just let one player build up a massive advantage from your cards and then try to win one-on-one. Remember they have a whole deck designed to advance their own strategy, and a majority of your deck is helping them too. You need some cards to reel them in at the end.
A few of your card choices seem a bit off to me. First up is
Primal Vigor, which is a very strong and good card. However, since it is a universal effect, it makes some of your cards strictly worse for you. Any of your “hunted” creatures will give double tokens,
Sheltering Ancient is now twice as good-for an opponent, etc. Now
Primal Vigor is giving you a disadvantage from your own cards, and at best your other mirror effects will simply
cancel out with the tokens you give your opponent.
Personal Sanctuary only has one card to protect you from, and that’s
Heartless Hidetsugu. How often are you planning to win through a combo with him? It's a useless card probably 90% of the time for you, and this deck doesn’t support digging for a combo (Hello
Gisela, Blade of Goldnight and
Heartless Hidetsugu).
Personal Sanctuary works a bit with
Ruric Thar, the Unbowed, but he’s another card that I don’t think fits too well with the deck. He’s more group slug than group hug, and you still have a decent amount of non-creature spells that he’ll hurt you for casting.
There are a couple cards that you have that I also think there are better (and still cheap) alternatives for. I’d like to see
Riot Control become
Illusionist’s Gambit. It still protects you from a combat step, but it can also potentially punish the attacking players board state or kill another player in the new combat step since the creatures
have to attack.
Seed the Land could strictly upgrade to
Zendikar’s Roil, although I’m guessing you chose
Seed the Land for group hug reasons?
You have a nice little enchantment sub-theme here. Therefore, I’d like to swap out
Prized Unicorn for
Noble Quarry. It has synergy with
Open the Vaults (since it’s going to definitely die pretty quickly) and
Simic Guildmage. You even get extra use out of it out of bestow. Also, it is 2G instead of 3G for the mana curve.
I have a similar argument for swapping
True Believer to
Aegis of the Gods. It has enchantment synergy and is 1W instead of WW, which makes a huge difference in a five color deck.
Anyway, there’s a lot here for a discussion on mana help that isn't about mana... oops. Guess I'll leave it here.
Hope I helped and happy deck building!