You might want to try more multiples of cards (play 4 of most cards).
Elvish Mystic instead of Druid of the Cowl because Elvish Mystic is a one drop.

Also replace 4 Forest with 4 Nykthos, Shrine to Nyx

You have no way to turn on Delirium for Traverse the Ulvenwald and very little of your sideboard makes sense?

Are you trying to be a "rush to Prime Titan" ramp deck or a "play unbeatable fatty" ramp deck or a "generate a ton of mana and loop something" ramp deck?

Thanks for the feedback, everyone!

Nykthos, Shrine to Nyx is in my aquireboard. I'm in college right now, so I'm limited in what I can spend on magic. It's definitely on the list!

I agree about Elvish Mystic vs Druid of the Cowl. The only reason cowl is in there is that I have one of those and I don't have any mystics right now. Next time I'm getting singles I'll pick up one or two.

As for delirium on Traverse the Ulvenwald, I know I don't have a way to activate it. Right now that card is mainly in there to get me lands, and to let me search my deck for the purposes of Panglacial Wurm. In retrospect, it might make sense to swap it out for lands or more 1 drop taps like Birds of Paradise.

Also, as I mentioned my sideboard is very much a work in progress. This is the first deck I've tried to make a sideboard for, and I haven't had a lot of time to look at stuff online to get to grips with the process. Any specific suggestions you'd have on that would be welcome :)

Utopia Sprawl comboes very well with your Arbor Elf. Garruk Wildspeaker is very good ramp too.

4x Utopia Sprawl to take advantage of the 4x Arbor Elf. 4x Garruk Wildspeaker should also be on the agenda. These cards allow 4 mana on turn 2 if you play t1 elf t2 land utopia sprawl. Garruk on turn 2 allows turn 3 7 mana or more depending if you can land nykthos turn 3.