If you want to get everything that IDW has published for their MLP Comic Line—minus the last three months—you are not going to find a better deal than the Humble Bundle that is going on right now.
For a donation of $15 USD, you get over three years worth of comic produced material.
For a donation of $25 USD, you also get and exclusive trade paperback collection featuring Sara Richard's DJing Pinkie Pie.
Don't forget to redeem your claim key before May 18th, 2016. If you decide to take the plunge:
Twitter: The Illustrious Q