Not much you can do on your skill level, but in general:
Play all-in strategies like mass hunts against fast expansions strategies. Saves you a lot of trouble.
Otherwise keep him from getting a 2nd expansion with your first hero, a couple of dryads and maybe Naga if you got her as 2nd hero. Place wisps on possible expansion spots.
Expand yourself while getting bears and a panda. Power-creep the panda, get a tp on him, so this bear squad can take on the tanks.
Upgrade natures blessing and build at least 3 aows at each of your base. Uproot and use them as meat shield. Eat trees to heal, uproot your expansion trees if necessary to reduce siege damage and eat trees. repair with wisps.
If he gets gryphons and later hawks, get a sufficient number of hippos. Your heroes + dryads + not-shackled hippos should be strong enough to take out hawks quickly, freeing your hippos to kill the gryphons. You only need ~4 dryads to dispell elementals and support. Otherwise bears + hippos is the way to go.
Leave if the Human gets his 2nd expansions up and secured with towers.