It's expensive as everything, but Gaea's Cradle
can help ramp, which is what this deck needs.
But on a more practical note, you definitely need to trim the amount of cards down by 19 or so. I know it's just for casual, but if you've got a specific strategy, it's better to keep the deck around 60 or so so that you can actually pull off what you're wanting to do instead of just relying on the luck of the draw. Personally, I'd probably either stick with Hydra's or Snakes, not both.
If sticking with Hydras, some ramp will definitely help. Nykthos, Shrine to Nyx is probably your best (affordable) bet. Aside from that, you'd probably want something that can cheat them out, like Quicksilver Amulet .
Looking through it, though, I think you could have a snake tribal thing going on and then ramp into a huge hydra, which is, erm, kinda what you're already doing....
I'd suggest removing several things:
Deadly Recluse - Sure, you might want him for sideboarding against flyers, but I think otherwise you won't need it.
Kashi-Tribe Warriors - There are better snakes to put in there.
Nessian Wilds Ravager - Like above, there are better Hydras to put in there.
Orochi Eggwatcher - Same
Orochi Ranger - Actually, I'm on the fence about this one - Keeping your opponent's creatures tapped is actually pretty useful.
Snake of the Golden Grove - Honestly, I'm just not wild about tribute mechanics. I think you could play something a little better - Giving you 4 life is a small price to pay to keep you from getting an undercosted fatty like that.
Fountain of Youth - Unless I'm missing some sort of crazy way to make this go infinite, I just don't think it's worth a slot in the deck. 2 Mana for one extra life a turn just feels like a waste.
Aspect of Wolf - Pretty good, but I think we could do better.
Roots - I see why you want it, but it might be better to sideboard.
Venom - Deathtouch is nice, but if you're playing green, you should make your guys so fat they don't need deathtouch - Then again, the flavor is strong on this one, so it's up to you.
Natural End - You probably want to move that to the sideboard more than anywhere else.
There's some more I'd suggest (you could probably just replace Terrifying Presence
, for instance), but eh. In the interest of saving time, I'll just say to cut most or all of the above and then maybe some of the others.
Now, as for what to put in there, I'll just list some suggestions (again, I'm not sure what your strategy is, but I'm assuming ramping into big stuff, so this is going off of that). Also keep in mind that you want to have more than just one of whichever creatures work the best for your deck.
Snakes:Sakiko, Mother of Summer - I'm not wild about this one, but if you're wanting to ramp, it's a solid choice if you get her out early and are going for a more aggro style.
Sakura-Tribe Elder - A great way to ramp and also a creature - A little better than Untamed Wilds (activate his ability at the end of the opponent's turn so that it'll be untapped when you start yours.)
Sakura-Tribe Springcaller - Free mana at the start of your turn.
Sachi, Daughter of Seshiro - I know you have it already, but it's a good one - Keep it, especially if you put in some of these other snake shaman creatures.
Orochi Leafcaller - Now, this is kinda complicated and I wouldn't suggest it unless you just really want to have a crazy combo deck, but this guy plus Sachi plus Freed from the Real = Infinite Mana. Otherwise, he just get's Sachi's bonus.
Kashi-Tribe Elite - I would recommend this fella mainly because you've got a lot of legendary snakes, and giving them hexproof would be aces.
Now, for Hydra's, you can keep what you have if you want, but I've always preferred using all of this crazy ramping to pull out exponentially huge guys, such as:
Hydra Broodmaster - If you get all of your rampers out, then you can have a ridiculous monstrosity ability.
Khalni Hydra - Again, if you have enough green fellas, he's free. Otherwise, you'd have plenty of ramp to get him out.
Primordial Hydra - This one can get absolutely ridiculous if you ramp properly.
Mistcutter Hydra - Mostly meant for sideboarding against blue, but hey, he's huge, uncounterable, and hasty, so that's always something.
Of course, aside from Hyrdas, there are other creatures that can be beastly with all of the ramping going on. Omnath, Locus of Mana not only get's buffed by your ramp, but let's you keep that mana floating in your mana pool.
Finally, and this is just a random suggetsion, but if you're playing ramp, I'd think that Asceticism
can be a great enchantment - You wouldn't need to worry about pumping all of your mana into a hyrda, only to have him get a big fat Doom Blade
to the face.
Anyway, sorry for the long-winded post. I just like the idea of Snakes & Hydras.
I like you're idea but you need to get creatures that are stronger and mana boosting cards to get those creatures out there faster.
I would instead of having 21 Forests, have 16 Forests and 4 Oran-Rief, the Vastwood .
Next these are the cards I would replace with the cards you have right now:1. 4-Llanorwar Elves for the 3 Arbor Elf . Better to have a creature be a mana source than control it. 2. 4 Garruk's Companion for 2 Nightshade Peddler and 2 Silklash Spider . Cheap but dangerous. 3. 1 Stranglerfoot Giest. They are good cards so have 4 of them. 4. 1 Yeva, Nature's Herald . for a total of 2. 5. Remove Ulvenwald Tracker . If he had more damage potential I would keep him but he doesn't. 6.1 Predator Ooze in addition to the 2 you have. 7. 4 Arbor Colossus . Remove the Primordial Hydra and the Silklash Spider . The colossus will take care of you're flying problem for the same cost and you have a heavy hitter. 8. Add 2 Wolfir Silverheart and 1 Wolfir Avenger in addition. They are good cards.
Now in regards to you're instants I would add more Fog and Giant Growth . I would remove the Sheltering Word , Terrifying Presence , and Ranger's Guile . Instead I would either add something that would find creatures in you're library, an enchantment giving them all additional boosts, or land searching cards.
I hope this helps.
I think Hunter's Insight would be better than Warriors' Lesson (it lets you draw more cards in almost every case). Also, Terrifying Presence would give you more combat tricks than Fog .(but its one more CMC could seriously set back your strategies, so I cannot say for sure).