Hello and welcome to Magic The Gathering. Going off of what Milmaster said previously he does have a point about the reliability and synergy aspects of deck building. That is why in my way of assisting you I will give you my recommendations one card at a time;
Ancient Crab - It's a decent upfront body and will save you some hits early game. If you had a way to keep giving it +1/+1 counters for example using
shapers of nature, then your crab would be mid-game viable as well.
Arborback Stomper - If you keep this card in the deck it would be solely for the life gain. But there are smaller creatures in Ixalan that are dinos and that can gain you a lot more health than this creature can do. It's ability only happens once. But creatures like
ravenous daggertooth will gain you health EVERY time it takes damage. That's a better long term investment and it being a dino gives it more utility.
Cancel - I don't have an issue with
cancel since it can stop pretty much anything. If you're going to include other cancelling spells then maybe run two copies of this spell.
Captain's Hook - This card is themed more towards the pirate creatures in the Ixalan sets. Even though it can be given to any creature it has that down side of killing any creature unequipped by it. If you're trying to be aggro with this deck or even combo-oriented in the build you don't want to have a card like this unless you are willing to let things go to the graveyard. If you really want you can sideboard it but turning your creatures into pirates without any support does nothing for the deck.
Cowl Prowler - This creature is big and it's a vanilla that has no effect, it's a plain monster. Now if you replaced it with say
snapping sailback, it's a dino that when it takes damage it gets a +1/+1 counter EVERY TIME it takes damage. So this is a creature that when it hits the board can stay on the field and hold its ground.
Crash the Ramparts - It's a good combat trick that you might want to run at 2-3 copies. It'll save your dinos or other big creatures in a pinch and trample is nice if you're being aggressive.
Crested Herdcaller - I would recommend adding more of these because they help fill up your board faster, it's a Dino so it's easier to play with your Dino support, AND it's strong on its own.
Drag Under - If you want a spell that does this I'd recommend finding a lower cost spell that does this same ability and that is also an INSTANT. This way you can use this ability on your opponent's turn as well.
Garruk's Horde - This actually would be a good card to keep in this deck. This will help you get your dinos on the field faster straight from the deck. Also since you're playing with the top card revealed you have some idea as to how to plan out your future turns.
Ghalta, Primal Hunger - This is a good card to have. If you an run it at 2 or even 3 it would be great for the deck. Just keep in mind that you can only have one copy on the field since it's a legendary creature.
Giant Spider - If it's the reach that you want then replace the spider with more grazing whiptails. Their creature type make them more synergistic with the deck, they're easier to get out and it's still a strong dino to have.
Grazing Whiptail - Run this card at 3-4 copies. It's stronger than the spider and the deck can actually support it.
Knight of the Stampede - Great card, run 3-4 copies of this card. Ir makes your other Dinos cheaper to play so that means you can play more stuff during your turn. IT's worth having.
Navigator's Ruin - This card needs to be removed because you're not focusing on the other person's deck.
Negate - I'd sideboard two and main board 2.
Oakenform - For enchantments I'd look at the
cartouche of strength or the
cartouche of knowledge instead. Yes +3/+3 is good but getting added abilities gives you more tricks to pull on your enemy.
Rabid Bite - Great card. Run 4 copies of it. It's a one sided fight card so basically you are removing an opponent's creature and your creature comes out unscathed. It's a god card to have in an arsenal full of big dinosaurs.
Ridgescale Tusker - Even though this creature is not a dino his ability can be used for your entire group. If you can bounce him or
flicker him out then he's ability will trigger again and again as long as he is
entering the battlefield. 1-2 copies.
River's Rebuke - pretty strong card, I'd play it at 2 copies at the most.
Rootwalla - I'm going to say no to the lizard and perhaps you'd want to include another dinosaur in it's place.
This way you get a creature that is supported by the deck AND it'll be easier to play.
Sea Legs - Not really a main board item but you can save it in the sideboard for unfavorable match-ups. Either that or just add more fight spells such as
pounce or hunt the week.
Spellweaver Eternal - It's a strong card but it doesn't have any support or place in this deck. Since a lot of stiff is big creatures, make stuff bigger then I'd say wither sideboard or remove from the deck.
Spidery Grasp - It's a good spell in the fact that it gives a creature reach AND it untaps the creature. A great combat trick for green.
Stalking Tiger - this is actually a good creature. I't not a dino but having 2 copies of it and giving them +1/+1 counters throughout the game will make it a
dangerous threat to the enemy.
Stampeding Rhino - It's a big creature but it doesn't do anything for the theme of the deck and how it operates.
Terrain Elemental - It doesn't really fit into the theme of the deck but it's got a good body for it's cost and it'll put in some work early to mid game. I'd have like 2-3 copies max.
Tricks of the Trade - Yes run multiple copies of this card. Having really big Dinosaurs that cannot be blocked will ALWAYS be a problem for the opponent.
Wind Drake - If you have other 3 drop flyers with abilities then there would be a reason to switch this one out.
Wing Snare - It's not a bad card for what it does. The problem is that this card is VERY specific with it's targets so it's a side board option. Maybe you can add Hadama's climb or switch it with
spire winder. It's a creature that for 1 more mana you get better stats AND it gets stronger mid-late game.
Druid of the Cowl - The druid is actually pretty good. It's a low drop that has good stats and if you're not blocking then you can use it for more mana. Both copies are worth keeping.
Highspire Infusion - This is good for it's mana cost but unless the deck is geared towards playing energy then I wouldn't recommend playing it. There are other cards in the Ixalan set that give you stat boosts AND give your creatures added abilities so that's worth looking into.
Crash the ramparts would be a worthy replacement.
Naga Vitalist - This is actually a pretty decent card to have in your deck. Since you're only running two colors you'll be good on double mana costed stuff and worse comes to worse it'll be a good body for blocking.
Seer of the Last Tomorrow - This card should be removed from the deck entirely. If you're not running a MILL strategy (making the opponent lose but running out of cards in their deck) then it does not need to be included in this build.
Wildgrowth Walker - This is a good card but you'd need to build the deck around the
explore mechanic to make it viable. Having other creatures for example like
ixalli's diviner,
emperor's vanguard,
merfolk branchwalker and such creatures would help this one creature's ability trigger multiple times. With the way the deck is going a Green/Blue fusion between merfolk and Dinosaurs probably wouldn't be too bad as long as the creatures and spells work well enough together.