Cards that have no immediate ETB effects are usually a bit too slow for constructed formats, but commander will embrace a card like Elder Gargaroth to its fullest. The only drawback is that it can't actually be your commander, since it's not legendary. However, you can still play it to three great effects.
The first and the third ability are probably the best: create a 3/3 green Best creature token and draw a card, respectively. Though, its second ability, gaining life, isn't bad either.
You can also give Elder Gargaroth haste for an immediate effect with commanders like Samut, Voice of Dissent, and Xenagos, God of Revels.