Hey mate!
First of, welcome to the world of EDH, in my opinion MTG's most fun format you can choose to play!
Rubinia Soulsinger is also a decent choice as your first commander due to the fact that she can work in many situations.
Just a bit of basic information since you are new to EDH:
The general can be a key component to your deck strategy. Most of the time it is either a core part or a really good supportive option for said strategy, while sometimes certain commanders are just played for their colors, what I personally don't really like doing myself.
Also, keep in mind that there is literally no end to 'pimp' or improve your deck, which makes it an even better format (while sh*t might get expensive if you dont keep attention).
Though there are a lot of cards which are considered 'bad' in most formats, and thus are cheap, while they are bonkers in EDH, but back to that point soon.
At fist glance, I really like your choice of cards, and I also think I see where you want to go with it, which would be, as you already said, to take advantage of your opponents permanents while protecting your board with enchantments and goodstuff creatures.
Let's go over some basic stuff and
bant staples first: [The cards I mention should be rather cheap and/or easy to trade for unless I f*ck up somewhere]
Green is the king of ramp in MTG, and it also is in commander.
Since your current average CMC is 3.83, I would suggest playing more ramp spells. They are cheap, both on mana and your wallet, and will
accelerate your gameplan by a couple of turns.
Your
Cultivate is a really good choice, but I would also add cards like
Kodama's ReachSearch for TomorrowFarseek and
Explosive VegetationAlso, mana dorks
run wild in green, if you want to up your creature count.
White has a lot of good enchantments and really good spot removal with cards like
Swords to Plowshares or
Path to Exile. Both are cheap and too good to pass by.
Aura of Silence,
Sigil of the empty Throne and
Sphere of Safety will protect you further and/or create angels to swing with in the air - don't underestimate 10+ 4/4 angels in the board.
Cards like Luminarch Ascention should help to protect you and also
serve as mana sponges, if you have for example open mana during the end of your opponents' turn.
While we talk about enchantments -
Bant has access to a really good card draw engine in synergy with said enchantments.
Cards like
Eidolon of Blossoms,
Enchantress's Presence and
Mesa Enchantress will draw you a ton of cards if not removed early. These also got reprinted in Commander 2018 if I am not mistaken, so they are cheap and easy to get.
As for Blue, we essentially talk about card draw and control.
I don't think that counterspells are something nessecairy in a casual group of EDH players, but I am sure you know your faire share of those, so I won't list them here.
There is one honorable mention, especially considering the 'steal your opponents' stuff' strategy:
Desertion - I don't think I need to explain why.
Just mix and match counters if you feel like you need them, and if not more power to you.
Sower of Temptation is also one of my favourite cards in MTG all together, I can't really count how many he won just by himself.
If you play the enchantment-draw cards I listed earlier, I don't think you need much blue card draw, but cards like
Treasure Cruise or
Brainstorm can help to draw into cards you might need in certain situations.
Some more input on your current build:
I personally would cut
Ajani Unyielding,
Shalai, Voice of Plenty,
Nissa, Voice of Zendikar,
Garruk's Horde,
Raff Capashen, Ship's Mage and
Oketra the TrueThose planeswalkers are just not performing well in EDH at all and need more cards to synergize with, what you can't really manage with your current
game plan. The creatures above don't work that well either, since your creature count is really low and thus they won't generate value most of the time.
Merieke Ri Berit is a simply cheaper version of Rubinia, while doing the same. I'd suggest to play both, and Merieke as your commander.
Reclamation Sage is a good card.
Empress Galina is a really good card as well. (~13$ price tag)
Serra's Sanctum will be bonkers in any enchantment heavy deck (VERY expensive, ~80$ price tag, but worth every penny. Only get this in a case where you REALLY want to keep that amount of enchantments!)
Nykthos, Shrine to Nyx is a cheaper but more versatile version of
Serra's Sanctum (~10$ price tag)
More steal:,
Control Magic,
Blatant Thievery,
Roil Elemental,
Bribery (~20$),
Thada Adel, Acquisitor,
Hypnotic Siren,
Cytoplast Manipulator,
Dominate,
Entrancing MelodyI could list some more, but I think I said enough for now.
Always feel free to message me about cards, I will help you as much as I can!
Also: EDH is a format where you can really play almost anything, never be afraif to try out cards, even if they don't seem that great at first glance. They might perform better then you could have anticipated!