Several suggestions based on my knowledge of the game:

Arbor Colossus : air killer when Monstrous plus he helps with the devotion count (+3).

Nylea, God of the Hunt : you do have several creatures that give your creatures trample, but not many have a pump up ability. Also it's indestructible, so that is always a plus.

Polukranos, World Eater : works good to have something that can kill off small creatures & get bigger in the process.

Primeval Bounty : It's one of my favorites, having 3 unique abilities that will work great with Yisan, the Wanderer Bard .

Nykthos, Shrine to Nyx : a Legendary devotion land. enough said.

Bramblecrush : helps against planeswalkers & other annoying non-creatures.

Voyaging Satyr : another mana dork is always good & works good with Nykthos, Shrine to Nyx .

Kalonian Tusker : 3/3 for 2 green, which is helpful towards your devotion.

Silklash Spider : Solves your flying problem.

Bow of Nylea : with all the mana you will have, doesn't hurt to have deathtouch when attacking.

Terra Stomper : an 8/8 for 6 mana with 3 green to the devotion & can't be countered. Great card to add that isn't too expensive.

Expensive cards:

Nissa, Worldwaker : one planeswalker that is worth the investment if your going to have an EDH deck.

Kalonian Hydra : a 4/4 that doubles his counters each time he attacks. ($7.93)

Asceticism : hexproof & regeneration for 2 mana. it's worth the investment.

Courser of Kruphix : greatest way to get lands out of the way, while gaining life, & on the important things.

Craterhoof Behemoth : a beast they better kill the second it comes out because he's that nasty. ($10.47)

Chord of Calling : one of the stronger cards out there to help Yisan, the Wanderer Bard with getting out those big boys on the battlefield. ($9.50 for the new version, $22.32 if it is the Ravnica version.

That's just a start.

Thanks for the suggestions. A lot of the cards you listed are out of my price range, at least for now. I try not to make a habit of buying big money standard cards for EDH/Commander decks since they always drop once they shift out. I'm going to dig through my cards for Asceticism and the others I accepted. They all seem legit and getable. If you have anymore budget friendly suggestions please list.

Will do. I get you on the grabbing standard cards at this point. If anything, local shops tend to have pretty low prices on certain cards, so check them out. If I think of some more cards, I'll tell you.

some more suggestions:

Elvish Archdruid : if you add a few more elves, this card is ideal for additional ramp.Spearbreaker Behemoth : creates indestructibles & is indestructible. May I say more?Nylea's Disciple : an option for if you which to gain life.Mistcutter Hydra : a great creature that has protection from blue & haste. It's only a consideration because if summoned by your commander, it comes in as a 0/0.Hydra Broodmaster : an interesting way to get tokens on the board. I don't know how well that works in commander, but it has potential from what I see when combined with Primeval Bounty .Reverent Hunter : a devotion guy, but is a risk when playing with multiple people due to all the removal & return out there that can get rid of him, but is a decent option if you can protect him.Hall of Triumph : a way to pump our creatures rather easily.Yeva, Nature's Herald : a cool legend that allows you to flash your green creatures in.Invasive Species : if you have a flash works well with cards that have 'entering the battlefield' activated abilities.Reclamation Sage : a great little sneak attack on an unsuspecting artifact or enchantment for 3.Hornet Nest : a funny card to play with.